java.lang.NullPointerException: Attempt to invoke virtual method 'int java.io.InputStream.read(byte[

最新推荐文章于 2022-09-08 15:42:02 发布
原创 最新推荐文章于 2022-09-08 15:42:02 发布 · 5.7k 阅读 · 1 ·
CC 4.0 BY-SA版权
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。

本文介绍了一个关于使用Java进行文件操作时遇到的问题：通过InputStream读取文件时出现异常的情况及其解决办法。文中提供了具体的代码示例，并解释了将InputStream替换为FileInputStream的原因。 
<span style="font-family: Arial, Helvetica, sans-serif;">				</span>
				InputStream inStream =getClass().getResourceAsStream(Path);
				FileOutputStream fs = new FileOutputStream(newPath);
				byte[] buffer = new byte[1024*5];
				while ((byteread = inStream.read(buffer )) != -1) {
					bytesum += byteread; 
					System.out.println(bytesum);
					fs.write(buffer, 0, byteread);
				}


				inStream.close();
</pre><pre name="code" class="java"><pre name="code" class="java"><pre name="code" class="java">在做文件操作的时候 <pre name="code" class="java">inStream.read(buffer ) 报的<span style="font-family: Arial, Helvetica, sans-serif;">这个</span><span style="font-family: Arial, Helvetica, sans-serif;">异常  原因是因为 </span><span style="font-family: Arial, Helvetica, sans-serif;">InputStream 不能被实例化</span>




解决方法
</pre><pre name="code" class="java">InputStream inStream =getClass().getResourceAsStream(Path); 改成 FileInputStream inStream = new FileInputStream(<span style="font-family: Arial, Helvetica, sans-serif;">Path</span><span style="font-family: Arial, Helvetica, sans-serif;">);</span>











                

        

    

    
  



    

      

        

            

              
                
                  rjq19961123
                
              
            

            

                关注
              
            

        

        

          
      

      










                



	

		

			

				
					
记录一次空指针异常的解决(java.lang.NullPointerException:Attempt to invoke virtual method)

				
			

			

				

					weixin_44287846的博客
				

				

					01-09
					
					2832
					
				

			

		

		

			
				
java.lang.NullPointerException:Attempt to invoke virtual method ’ xxxxxx’  on a null object reference

根据AS的提示定位到student.getName()方法上
先尝试使用Log.e()输出student对象
控制台打印出 -> null
最后发现获取student对象失败了
public static Student getLoginer() {
        if (BmobUser.isL

			
		

	



                

            
              



	

		

			

				
					
Android音乐Attempt to invoke virtual method ‘java.lang.String android.content.Intent.getStringExtra异常

				
			

			

				

					weixin_52785320的博客
				

				

					08-06
					
					5029
					
				

			

		

		

			
				
在开发音乐播放器过程中又出现了一点问题，起初查看Log日志，提示如下图所示的异常信息......

			
		

	



              


  
              

                


	

		

			

				
					
CRASH问题：java.lang.NullPointerException

				
			

			

				

					01-21
				

			

		

		

			
				
java.lang.NullPointerException: Attempt to invoke virtual method ‘void android.widget.ImageView.setImageResource(int)’ on a null object reference
今天在家练习ListView的时候，遇到一个java.lang.NullPointerException的空指针异常，log如下：
2020-05-10 15:40:29.249 20436-20436/? E/k.myapplicatio: Unknown bits set in runtime_flag

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.content.Intent.getI...

				
			

			

				

					aaLiweipeng的博客
				

				

					11-11
					
					3098
					
				

			

		

		

			
				

  
    
            这个报错比较骚，完全只是因为Intent没有写好而已，下面是错误的写法（最好不要在方法外赋值）：







进入本活动时即刻报错：







11-10 18:23:24.231 17152-17152/? E/AndroidRuntime: FATAL EXCEPTION: main
                               ...

			
		

	



		

			
		



	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()

				
			

			

				

					comde的博客
				

				

					12-26
					
					2024
					
				

			

		

		

			
				
运行就报空指针找了很久也没发现问题，我是应该初学者求大佬帮忙看看





			
		

	





	

		

			

				
					
java.lang.NullPointerException Attempt to invoke virtual method xxx on a null object reference

				
			

			

				

					m0_54883970的博客
				

				

					05-28
					
					331
					
				

			

		

		

			
				
此刻，我有一百万个不明白，写了这么久的代码，代码如此正确、优美，怎么个就报空指针呢？

布局代码
<TextView
        android:id="@+id/id_tv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="texts"
        android:layout_alignParentBottom="tr

			
		

	





	

		

			

				
					
Attempt to invoke virtual method ‘...’ on a null object reference 错误，Activity页面跳转失败

				
			

			

				

					black_ct的博客
				

				

					02-07
					
					2446
					
				

			

		

		

			
				
两个都是在 Activity实现跳转时出现的BUG，导致App的闪退

BUG1

错误信息：



关键信息就在这：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.DisplayActivity}: ja...

			
		

	





	

		

			

				
					
package com.example.heart_oxygen_monitoring_system;

import android.Manifest;
import android.annotation.SuppressLint;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import androidx.activity.EdgeToEdge;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import com.google.gson.Gson;
import com.google.gson.annotations.SerializedName;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

import okhttp3.OkHttpClient;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
import retrofit2.http.Body;
import retrofit2.http.Header;
import retrofit2.http.POST;

public class MainActivity extends AppCompatActivity {

    // UI组件
    private TextView tvConnectionStatus;
    private TextView tvHeartRate;
    private TextView tvSpO2;
    private TextView tvTemperature;
    private Button btnScan;
    private EditText etQuestion;
    private Button btnAskAI;
    private TextView tvAIResponse;

    // 蓝牙相关
    private BluetoothHelper bluetoothHelper;
    private BluetoothAdapter bluetoothAdapter;
    private BluetoothSocket bluetoothSocket;
    private ConnectedThread connectedThread;
    private final ArrayList<BluetoothDevice> deviceList = new ArrayList<>();

    // AI相关
    private ApiService apiService;
    private int currentHeartRate = 0;
    private int currentSpO2 = 0;
    private float currentTemperature = 0.0f;

    //权限和请求码
    private static final int REQUEST_ENABLE_BT = 1;
    private static final int REQUEST_BLUETOOTH_PERMISSIONS = 2;
    private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
    private static final String TAG = "MainActivity";

    private ActivityResultLauncher<Intent> bluetoothEnableLauncher;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);

        // 初始化结果监听器
        bluetoothEnableLauncher = registerForActivityResult(
                new ActivityResultContracts.StartActivityForResult(),
                result -> {
                    if (result.getResultCode() == RESULT_OK) {
                        // 用户启用了蓝牙
                        startDeviceDiscovery();
                    } else {
                        Toast.makeText(this, "蓝牙未启用", Toast.LENGTH_SHORT).show();
                    }
                });

        initViews();
        initBluetooth();
        setupButtonListeners();
        initAIService();
    }

    private void initViews() {
        tvConnectionStatus = findViewById(R.id.tvConnectionStatus);
        tvHeartRate = findViewById(R.id.tvHeartRate);
        tvSpO2 = findViewById(R.id.tvSpO2);
        tvTemperature = findViewById(R.id.tvTemperature);
        btnScan = findViewById(R.id.btnScan);
        etQuestion = findViewById(R.id.etQuestion);
        btnAskAI = findViewById(R.id.btnAskAI);
        tvAIResponse = findViewById(R.id.tvAIResponse);

        updateBluetoothStatus(false);
        resetDataDisplay();
    }

    private void resetDataDisplay() {
        tvHeartRate.setText("--");
        tvSpO2.setText("--");
        tvTemperature.setText("--");
    }

    private void initBluetooth() {
        bluetoothHelper = new BluetoothHelper(this);
        bluetoothAdapter = bluetoothHelper.getBluetoothAdapter();

        if (!bluetoothHelper.isBluetoothSupported()) {
            Toast.makeText(this, "设备不支持蓝牙", Toast.LENGTH_SHORT).show();
            return;
        }

        // 注册广播接收器
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(deviceReceiver, filter);
    }

    private void initAIService() {
        // 创建HTTP日志拦截器
        HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
        loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

        // 创建OkHttpClient
        OkHttpClient client = new OkHttpClient.Builder()
                .addInterceptor(loggingInterceptor)
                .build();

        // 创建Retrofit实例
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://192.168.88.105:8880/") // 替换为你的RAGFlow服务器地址
                .client(client)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        // 创建API服务
        apiService = retrofit.create(ApiService.class);
    }

    private void setupButtonListeners() {
        btnScan.setOnClickListener(v -> {
            if (checkPermissions()) {
                if (!bluetoothHelper.isBluetoothEnabled()) {
                    requestEnableBluetooth();
                } else {
                    startDeviceDiscovery();
                }
            }
        });

        btnAskAI.setOnClickListener(v -> {
            String question = etQuestion.getText().toString().trim();
            if (!question.isEmpty()) {
                askAI(question);
            } else {
                Toast.makeText(this, "请输入问题", Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void requestEnableBluetooth() {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        bluetoothEnableLauncher.launch(enableBtIntent);
    }

    private void startDeviceDiscovery() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_SCAN)
                != PackageManager.PERMISSION_GRANTED) {
            return;
        }

        deviceList.clear();
        if (bluetoothAdapter.isDiscovering()) {
            bluetoothAdapter.cancelDiscovery();
        }

        if (bluetoothAdapter.startDiscovery()) {
            Toast.makeText(this, "正在搜索STM32设备...", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "搜索启动失败", Toast.LENGTH_SHORT).show();
        }
    }

    private final BroadcastReceiver deviceReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                if (ActivityCompat.checkSelfPermission(MainActivity.this,
                        Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED) {
                    return;
                }

                // 只添加名称包含"STM32"的设备
                assert device != null;
                if (device.getName() != null && device.getName().contains("STM32")) {
                    if (!deviceList.contains(device)) {
                        deviceList.add(device);
                        showDeviceSelectionDialog();
                    }
                }
            }
        }
    };

    private void showDeviceSelectionDialog() {
        if (deviceList.isEmpty()) return;

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("选择STM32设备");

        ArrayList<String> deviceNames = new ArrayList<>();
        for (BluetoothDevice device : deviceList) {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT)
                    != PackageManager.PERMISSION_GRANTED) {
                continue;
            }
            deviceNames.add(device.getName() + "\n" + device.getAddress());
        }

        builder.setItems(deviceNames.toArray(new String[0]), (dialog, which) -> connectToDevice(deviceList.get(which)));
        builder.setNegativeButton("取消", null);
        builder.show();
    }

    private void connectToDevice(BluetoothDevice device) {
        try {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT)
                    != PackageManager.PERMISSION_GRANTED) {
                return;
            }

            bluetoothSocket = device.createRfcommSocketToServiceRecord(MY_UUID);

            new Thread(() -> {
                try {
                    bluetoothSocket.connect();
                    runOnUiThread(() -> {
                        updateBluetoothStatus(true);
                        Toast.makeText(MainActivity.this,
                                "已连接到: " + device.getName(),
                                Toast.LENGTH_SHORT).show();
                    });

                    // 启动数据接收线程
                    connectedThread = new ConnectedThread(bluetoothSocket);
                    connectedThread.start();

                } catch (IOException e) {
                    runOnUiThread(() -> {
                        updateBluetoothStatus(false);
                        Toast.makeText(MainActivity.this,
                                "连接失败: " + e.getMessage(),
                                Toast.LENGTH_SHORT).show();
                    });
                }
            }).start();

        } catch (IOException e) {
            Toast.makeText(this, "创建连接失败", Toast.LENGTH_SHORT).show();
        }
    }

    private class ConnectedThread extends Thread {
        private final InputStream mmInStream;
        private final byte[] mmBuffer = new byte[1024];

        public ConnectedThread(BluetoothSocket socket) {
            InputStream tmpIn = null;
            try {
                tmpIn = socket.getInputStream();
            } catch (IOException e) {
                Log.e(TAG, "获取输入流失败", e);
            }
            mmInStream = tmpIn;
        }

        public void run() {
            StringBuilder receivedData = new StringBuilder();

            while (!Thread.interrupted()) {
                try {
                    int bytes = mmInStream.read(mmBuffer);
                    String chunk = new String(mmBuffer, 0, bytes);
                    receivedData.append(chunk);

                    // 检查是否收到完整数据包
                    if (chunk.contains("\n")) {
                        final String completeData = receivedData.toString().trim();
                        receivedData.setLength(0);

                        new Handler(Looper.getMainLooper()).post(() ->
                                processSTM32Data(completeData));
                    }

                } catch (IOException e) {
                    Log.e(TAG, "连接断开", e);
                    runOnUiThread(() -> {
                        updateBluetoothStatus(false);
                        Toast.makeText(MainActivity.this,
                                "与设备断开连接", Toast.LENGTH_SHORT).show();
                    });
                    break;
                }
            }
        }
    }

    private void processSTM32Data(String rawData) {
        // 示例数据格式: "HR:75,SpO2:98,Temp:36.5"
        try {
            String[] pairs = rawData.split(",");
            for (String pair : pairs) {
                String[] keyValue = pair.split(":");
                if (keyValue.length == 2) {
                    String key = keyValue[0].trim();
                    String value = keyValue[1].trim();

                    switch (key) {
                        case "HR":
                            updateHeartRate(value);
                            break;
                        case "SpO2":
                            updateOxygenLevel(value);
                            break;
                        case "Temp":
                            updateTemperature(value);
                            break;
                    }
                }
            }
        } catch (Exception e) {
            Log.e(TAG, "数据解析错误: " + rawData, e);
        }
    }

    private void updateHeartRate(String value) {
        tvHeartRate.setText(value);
        try {
            currentHeartRate = Integer.parseInt(value);
            tvHeartRate.setTextColor(currentHeartRate < 60 || currentHeartRate > 100 ? Color.RED :
                    ContextCompat.getColor(this, R.color.primary));
        } catch (NumberFormatException e) {
            tvHeartRate.setTextColor(ContextCompat.getColor(this, R.color.primary));
        }
    }

    private void updateOxygenLevel(String value) {
        tvSpO2.setText(value);
        try {
            currentSpO2 = Integer.parseInt(value);
            tvSpO2.setTextColor(currentSpO2 < 90 ? Color.RED :
                    ContextCompat.getColor(this, R.color.primary));
        } catch (NumberFormatException e) {
            tvSpO2.setTextColor(ContextCompat.getColor(this, R.color.primary));
        }
    }

    private void updateTemperature(String value) {
        tvTemperature.setText(value);
        try {
            currentTemperature = Float.parseFloat(value);
        } catch (NumberFormatException e) {
            // 忽略解析错误
        }
    }

    private void updateBluetoothStatus(boolean isConnected) {
        if (isConnected) {
            tvConnectionStatus.setText("蓝牙状态: 已连接");
            tvConnectionStatus.setTextColor(ContextCompat.getColor(this, R.color.green));
            btnScan.setVisibility(View.GONE);
        } else {
            tvConnectionStatus.setText("蓝牙状态: 未连接");
            tvConnectionStatus.setTextColor(ContextCompat.getColor(this, R.color.red));
            btnScan.setVisibility(View.VISIBLE);
            resetDataDisplay();
        }
    }

    private void askAI(String question) {
        // 显示加载中
        tvAIResponse.setText("思考中...");

        // 构建请求
        ChatRequest.Message userMessage = new ChatRequest.Message("user", question);
        List<ChatRequest.Message> messages = new ArrayList<>();
        messages.add(userMessage);

        ChatRequest request = new ChatRequest();
        request.setModel("deepseek-r1:1.5b"); // 与你RAGFlow中配置的模型一致
        request.setMessages(messages);
        request.setStream(false);

        // 异步调用
        Call<ApiResponse> call = apiService.sendMessage("Bearer your_api_key_if_any", request);
        call.enqueue(new Callback<ApiResponse>() {
            @SuppressLint("SetTextI18n")
            @Override
            public void onResponse(@NonNull Call<ApiResponse> call, @NonNull Response<ApiResponse> response) {
                if (response.isSuccessful() && response.body() != null) {
                    // 提取AI回复内容
                    String aiResponse = response.body().getChoices().get(0).getMessage().getContent();
                    tvAIResponse.setText(aiResponse);
                } else {
                    tvAIResponse.setText("抱歉，请求失败: " + response.message());
                }
            }

            @SuppressLint("SetTextI18n")
            @Override
            public void onFailure(@NonNull Call<ApiResponse> call, @NonNull Throwable t) {
                tvAIResponse.setText("网络错误: " + t.getMessage());
            }
        });
    }

    private void generateHealthAdvice() {
        @SuppressLint("DefaultLocale") String healthQuery = String.format(
                "我的心率是%d bpm，血氧是%d%%，体温是%.1f°C。请分析我的健康状况并提供简要建议。",
                currentHeartRate, currentSpO2, currentTemperature
        );

        askAI(healthQuery);
    }

    private boolean checkPermissions() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            if (checkSelfPermission(Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED ||
                    checkSelfPermission(Manifest.permission.BLUETOOTH_SCAN) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{
                        Manifest.permission.BLUETOOTH_CONNECT,
                        Manifest.permission.BLUETOOTH_SCAN,
                        Manifest.permission.ACCESS_FINE_LOCATION
                }, REQUEST_BLUETOOTH_PERMISSIONS);
                return false;
            }
        } else {
            if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{
                        Manifest.permission.ACCESS_FINE_LOCATION
                }, REQUEST_BLUETOOTH_PERMISSIONS);
                return false;
            }
        }
        return true;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_BLUETOOTH_PERMISSIONS) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startDeviceDiscovery();
            } else {
                Toast.makeText(this, "需要权限才能使用蓝牙功能", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_ENABLE_BT) {
            if (resultCode == RESULT_OK) {
                startDeviceDiscovery();
            } else {
                Toast.makeText(this, "蓝牙未启用", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @SuppressLint("MissingPermission")
    @Override
    protected void onDestroy() {
        super.onDestroy();

        // 取消设备发现
        if (bluetoothAdapter != null && bluetoothAdapter.isDiscovering()) {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_SCAN)
                    == PackageManager.PERMISSION_GRANTED) {
                bluetoothAdapter.cancelDiscovery();
            }
        }

        // 注销广播接收器
        try {
            unregisterReceiver(deviceReceiver);
        } catch (IllegalArgumentException e) {
            Log.e(TAG, "接收器未注册");
        }

        // 关闭连接
        if (connectedThread != null) {
            connectedThread.interrupt();
        }
        if (bluetoothSocket != null) {
            try {
                bluetoothSocket.close();
            } catch (IOException e) {
                Log.e(TAG, "关闭socket失败", e);
            }
        }
    }

    // API请求和响应数据模型
    public static class ChatRequest {
        private String model;
        private List<Message> messages;
        private boolean stream = false;

        public String getModel() {
            return model;
        }

        public void setModel(String model) {
            this.model = model;
        }

        public List<Message> getMessages() {
            return messages;
        }

        public void setMessages(List<Message> messages) {
            this.messages = messages;
        }

        public boolean isStream() {
            return stream;
        }

        public void setStream(boolean stream) {
            this.stream = stream;
        }

        public static class Message {
            private String role;
            private String content;

            public Message(String role, String content) {
                this.role = role;
                this.content = content;
            }

            public String getRole() {
                return role;
            }

            public void setRole(String role) {
                this.role = role;
            }

            public String getContent() {
                return content;
            }

            public void setContent(String content) {
                this.content = content;
            }
        }
    }

    public static class ApiResponse {
        private String id;
        private List<Choice> choices;

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public List<Choice> getChoices() {
            return choices;
        }

        public void setChoices(List<Choice> choices) {
            this.choices = choices;
        }

        public static class Choice {
            private Message message;

            public Message getMessage() {
                return message;
            }

            public void setMessage(Message message) {
                this.message = message;
            }

            public static class Message {
                private String role;
                private String content;

                public String getRole() {
                    return role;
                }

                public void setRole(String role) {
                    this.role = role;
                }

                public String getContent() {
                    return content;
                }

                public void setContent(String content) {
                    this.content = content;
                }
            }
        }
    }

    // API服务接口
    public interface ApiService {
        @POST("/api/v1/chat/completions") // 根据RAGFlow实际API端点调整
        Call<ApiResponse> sendMessage(
                @Header("Authorization") String auth,
                @Body ChatRequest request
        );
    }
}
根据报错信息给我修改一下
FATAL EXCEPTION: main
                                                                                                    Process: com.example.heart_oxygen_monitoring_system, PID: 1806
                                                                                                    java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.List.get(int)' on a null object reference
                                                                                                    	at com.example.heart_oxygen_monitoring_system.MainActivity$2.onResponse(MainActivity.java:430)
                                                                                                    	at retrofit2.DefaultCallAdapterFactory$ExecutorCallbackCall$1.lambda$onResponse$0$retrofit2-DefaultCallAdapterFactory$ExecutorCallbackCall$1(DefaultCallAdapterFactory.java:89)
                                                                                                    	at retrofit2.DefaultCallAdapterFactory$ExecutorCallbackCall$1$$ExternalSyntheticLambda0.run(D8$$SyntheticClass:0)
                                                                                                    	at android.os.Handler.handleCallback(Handler.java:973)
                                                                                                    	at android.os.Handler.dispatchMessage(Handler.java:100)
                                                                                                    	at android.os.Looper.loopOnce(Looper.java:282)
                                                                                                    	at android.os.Looper.loop(Looper.java:387)
                                                                                                    	at android.app.ActivityThread.main(ActivityThread.java:9500)
                                                                                                    	at java.lang.reflect.Method.invoke(Native Method)
                                                                                                    	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:600)
                                                                                                    	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1005)

					
最新发布

				
			

			

				

					09-04
				

			

		

		

			
				
`java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.List.get(int)' on a null object reference` 错误表明在代码中尝试对一个 `null` 对象调用 `List` 接口的 `get...

			
		

	





	

		

			

				
					
深度学习Java的类加载机制

				
			

			

				

					cout_s的博客
				

				

					09-04
					
					738
					
				

			

		

		

			
				
java的类加载机制

前言
学生时代应抱着问题去学习一门语言，例如：在学习java语言的过程中，我遇到过java主方法main里面参数到底是存的什么？还有java语言的Object是如何成为所有类的父类的？java虚拟机到底如何解析字节码文件的？java是纯面向对象编程语言那么它的类是怎样的加载过程？今天我就带着大家一探究竟。
步入正题
首先我们都熟悉DOS界面去执行我们编写的源码，第一步使用javac  xxx.java命令,这个命令其实就是调用java的编译器，每一门语言都有自己的编译器，有的源文件是

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method ‘int java.lang.String.length()‘ on

				
			

			

				

					王哥小跟班的博客
				

				

					09-08
					
					1772
					
				

			

		

		

			
				
在做简单计算器案例时，加了这行代码突然报错

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()'

				
			

			

				

					weixin_41575100的博客
				

				

					01-02
					
					1万+
					
				

			

		

		

			
				
int与integer的区别从大的方面来说就是基本数据类型与其包装类的区别：

int 是基本类型，直接存数值，而integer是对象，用一个引用指向这个对象

获取到integer必须先判null再转int


public Integer getContactType() {
    return contactType;
}

public String getContactT

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method ‘int java.lang.Integer.intValue()‘

				
			

			

				

					T_Y_F_的博客
				

				

					09-07
					
					3565
					
				

			

		

		

			
				
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()'

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method xxx on a null object reference

					
热门推荐

				
			

			

				

					小红妹
				

				

					11-22
					
					10万+
					
				

			

		

		

			
				
此刻，我有一百万个想不明白，写了这么久的代码，代码如此正确、优美，怎么个就报空指针呢？

			
		

	





	

		

			

				
					
Android异常：java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.len

				
			

			

				

					qq_41167962的博客
				

				

					08-12
					
					5万+
					
				

			

		

		

			
				
Android studio 异常：java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference

    这种标题的异常有很多种，我所知道的有的是布局出错，有的是Java代码的错误。不管是哪种错误应该都是...

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method ‘

				
			

			

				

					zy的博客
				

				

					03-29
					
					1878
					
				

			

		

		

			
				
这几天写登录界面的时候，一直都被一个问题困扰。
当切换到验证码登录的时候，记住密码对话框应该被隐藏。
这里用到了
先定义成员变量
 CheckBox checkBox_remember_password;

//在方法中进行findViewById()
checkBox_remember_password=findViewById(R.id.checkBox_remember_password);...

			
		

	





	

		

			

				
					
java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File

				
			

			

				

					csdn9228的博客
				

				

					04-07
					
					1万+
					
				

			

		

		

			
				
java.lang.RuntimeException: Unable to resume activity {com.example.senior/com.example.senior.ShoppingCartActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File com....

			
		

	





	

		

			

				
					
java.lang.nullpointerexception: attempt to invoke virtual method 'void java.

				
			

			

				

					06-06
				

			

		

		

			
				
java.lang.NullPointerException: attempt to invoke virtual method 'void java.lang.StringBuilder.append(java.lang.String)' on a null object reference异常是Java中常见的错误之一。简单地说，这个异常表示...

			
		

	



              




          




        



    





    



      

      

        
      

      





	

		评论	
	

  
	




  

    

      添加红包
      
    

    

      

        
        

          
          
        

        
请填写红包祝福语或标题

      

      

        
        

          
          个
        

        
红包个数最小为10个

      

      

        
        

          
          元
        

        
红包金额最低5元

      

      

        
        

          当前余额3.43元
          前往充值 >
        

      

      

        

          需支付：10.00元
        

        
        
      

    

  





  

    
    
  

  

    
    
  








  

    

      

        

          

            
            
成就一亿技术人!

          

          

        

        

          

          

            领取后你会自动成为博主和红包主的粉丝
            规则
          

        

      

      

        

          

            
              
            
            

              
hope_wisdom
 发出的红包
            

          

        

        

          

          

          

        

      

    

    

  



      
      

      
实付元

      
使用余额支付

      

        

          

            
            点击重新获取
          

        

        
扫码支付

      

      

        
          
            
          
          
        
      

      

        
        钱包余额
          0
          

            
            

              

                
抵扣说明：

                
 1.余额是钱包充值的虚拟货币，按照1:1的比例进行支付金额的抵扣。
 2.余额无法直接购买下载，可以购买VIP、付费专栏及课程。

              

            

          

      

      余额充值