Android将byte数组写入文件

最新推荐文章于 2025-06-01 18:29:20 发布

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最新推荐文章于 2025-06-01 18:29:20 发布

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分类专栏： android 学习文章标签： android

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本文展示了如何在Android中将byte数组写入文件，并强调了动态权限申请的重要性。通过实例代码，详细解释了如何将byte数组转换为16进制数据并保存到文件，提供了解决此类问题的参考。

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1.先看看效果图吧：

打印的日志：

/com.example.administrator.testz E/TAG: getCrashFilePath: /storage/emulated/0/Testz/Crash/

2.写入文件当然需要先添加权限

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

3.开始写byte数组

package com.example.administrator.testz;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Locale;

public class MainActivity extends AppCompatActivity {
    private static final String CRASH_REPORTER_EXTENSION = ".txt";
    private Button btn;

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

        btn = (Button) findViewById(R.id.btn_write);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    writeBytesToFile();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }


    public void writeBytesToFile() throws IOException {
        StringBuilder sb = new StringBuilder();
        @SuppressLint("SimpleDateFormat") SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.CHINA);
        String now = sdf.format(new Date());
        sb.append("TIME:").append(now);
        String s = "69 00 01 03 AA 16";
        byte[] bs = s.getBytes();
        OutputStream out = new FileOutputStream(getCrashFilePath(MainActivity.this) + now + CRASH_REPORTER_EXTENSION);
        InputStream is = new ByteArrayInputStream(bs);
        byte[] buff = new byte[1024];
        int len = 0;
        while ((len = is.read(buff)) != -1) {
            out.write(buff, 0, len);
        }
        is.close();
        out.close();
    }

    /**
     * 获取文件夹路径
     *
     * @param context
     * @return
     */
    private static String getCrashFilePath(Context context) {
        String path = null;
        try {
            path = Environment.getExternalStorageDirectory().getCanonicalPath() + "/"
                    + context.getResources().getString(R.string.app_name) + "/Crash/";
            File file = new File(path);
            if (!file.exists()) {
                file.mkdirs();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        Log.e("TAG", "getCrashFilePath: " + path);
        return path;
    }
}

注意保存文件，要做动态权限申请

2.把byte转成16进制的数据，在存，大家以后碰到类似的需求时，一定要学会灵活应用

package com.example.administrator.testz;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Locale;

public class MainActivity extends AppCompatActivity {
    private static final String CRASH_REPORTER_EXTENSION = ".txt";
    private Button btn;

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

        btn = (Button) findViewById(R.id.btn_write);


        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    writeBytesToFile();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }


    /**
     * 字节数组转成16进制表示格式的字符串
     *
     * @param byteArray 需要转换的字节数组
     * @return 16进制表示格式的字符串
     **/
    public static String toHexString(byte[] byteArray) {
        if (byteArray == null || byteArray.length < 1)
            throw new IllegalArgumentException("this byteArray must not be null or empty");

        final StringBuilder hexString = new StringBuilder();
        for (int i = 0; i < byteArray.length; i++) {
            if ((byteArray[i] & 0xff) < 0x10)//0~F前面不零
                hexString.append("0");
            hexString.append(Integer.toHexString(0xFF & byteArray[i]));
        }
        return hexString.toString().toLowerCase();
    }

    public void writeBytesToFile() throws IOException {
        StringBuilder sb = new StringBuilder();
        @SuppressLint("SimpleDateFormat") SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.CHINA);
        String now = sdf.format(new Date());
        sb.append("TIME:").append(now);
        byte[] datas = new byte[]{0x69, 0x01, 0x05, 0x03, 0x65, 0x16};
        byte[] bs = toHexString(datas).getBytes();
        OutputStream out = new FileOutputStream(getCrashFilePath(MainActivity.this) + now + CRASH_REPORTER_EXTENSION);
        InputStream is = new ByteArrayInputStream(bs);
        byte[] buff = new byte[1024];
        int len = 0;
        while ((len = is.read(buff)) != -1) {
            out.write(buff, 0, len);
        }
        is.close();
        out.close();
    }

    /**
     * 获取文件夹路径
     * @param context
     * @return
     */
    private static String getCrashFilePath(Context context) {
        String path = null;
        try {
            path = Environment.getExternalStorageDirectory().getCanonicalPath() + "/"
                    + context.getResources().getString(R.string.app_name) + "/Crash/";
            File file = new File(path);
            if (!file.exists()) {
                file.mkdirs();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        Log.e("TAG", "getCrashFilePath: " + path);
        return path;
    }
}