HttpURLConnection加载网络图片

最新推荐文章于 2025-06-11 13:06:20 发布

原创最新推荐文章于 2025-06-11 13:06:20 发布 · 937 阅读

CC 4.0 BY-SA版权

这篇博客介绍了如何利用HttpURLConnection在Android中加载网络图片，强调了使用Bitmap的重要性以及处理耗时操作的方法，如使用Handler或AsyncTask。还详细说明了在Android 6.0及以上版本中进行权限设置的步骤。

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使用HttpURLConnection加载网络图片

效果图展示

这里写图片描述

注意点：

01、加载网络图片需要用到Bitmap

02、加载网络图片有时候比较耗时，可以用Handler或AsyncTask来解决

代码展示（AsyncTask）

//在xml文件中
<Button
        android:id="@+id/main2_btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="加载图片"/>
    <ImageView
        android:id="@+id/main2_image"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

//在Activity中

public class Main2Activity extends AppCompatActivity {

    private Button showBtn;
    private ImageView webimgView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        bindID();

        showBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ImgLoadTask imgLoadTask=new ImgLoadTask(webimgView);
                imgLoadTask.execute("http://p2.so.qhimgs1.com/bdr/_240_/t01b20aa81f9cd5a5f2.jpg");//execute里面是图片的地址
            }
        });
    }

    private void bindID() {
        showBtn=findViewById(R.id.main2_btn);
        webimgView=findViewById(R.id.main2_image);
    }

        }

//在ImgLoadTask.java中
public class ImgLoadTask extends AsyncTask<String,Integer,Bitmap>{

    private ImageView imageView;

    //为什么要加一个构造方法--有传值的需求
    public  ImgLoadTask(ImageView imageView1){
        this.imageView=imageView1;
    }

    @Override
    protected Bitmap doInBackground(String... strings) {

        //加载网络图片，最后获取到一个Bitmap对象，返回Bitmap对象
        Bitmap bmp=null;
        try {
        //创建URL对象
            URL url=new URL(strings[0]);
            //通过URL对象得到HttpURLConnection
            HttpURLConnection connection= (HttpURLConnection) url.openConnection();（//这边需要强制转换）
            //得到输入流
            InputStream inputStream=connection.getInputStream();
            //把输入流转换成Bitmap类型对象
           bmp= BitmapFactory.decodeStream(inputStream);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return bmp;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        super.onPostExecute(bitmap);
        imageView.setImageBitmap(bitmap);
    }
}

二、使用HttpURLConnection下载网络图片并显示

效果展示图

这里写图片描述

代码展示

//在布局文件中
 <Button
        android:id="@+id/web_downbtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="下载图片"/>
    <ImageView
        android:id="@+id/down_img"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/web_downbtn"
        />

如果要在安卓6.0以上运行，要进行权限设置（以下代码就是6.0以上的）

首先在build.gradle中编译

compile ‘com.master.android:permissionhelper:1.3’

然后在Activity中写入以下代码

public class HelloActivity extends AppCompatActivity {

    private String TAG = "HelloActivity";
    private PermissionHelper permissionHelper;

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

        permissionHelper = new PermissionHelper(this, new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE}, 100);
        permissionHelper.request(new PermissionHelper.PermissionCallback() {
            @Override
            public void onPermissionGranted() {
                //全都授权
                Log.e(TAG,"onPermissionGranted...");
            }

            @Override
            public void onIndividualPermissionGranted(String[] grantedPermission) {
                //某个授权
                Log.e(TAG,"onIndividualPermissionGranted() called with: grantedPermission = [" + TextUtils.join(",",grantedPermission) + "]");
            }

            @Override
            public void onPermissionDenied() {
                //某个拒绝
                Log.e(TAG,"onPermissionDenied...");
            }

            @Override
            public void onPermissionDeniedBySystem() {
                //用户选择了"不再询问"后，点击"拒绝按钮"，执行此方法
                Log.e(TAG,"onPermissionDeniedBySystem...");
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (permissionHelper != null) {
            permissionHelper.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

}

//在Activity中
public class Main5Activity extends AppCompatActivity {

    private Button downbtn;
    private ImageView imageView;
    private String TAG = "HelloActivity";
    private PermissionHelper permissionHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main5);

        permissionHelper = new PermissionHelper(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 100);
        permissionHelper.request(new PermissionHelper.PermissionCallback() {
            @Override
            public void onPermissionGranted() {
                //全都授权

                bindID();

                downbtn.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        DownTask downTask=new DownTask(Main5Activity.this,imageView);
                        downTask.execute("http://p5.so.qhimgs1.com/bdr/_240_/t017e2f48ce6aeed19b.jpg","qhjwp.jpg");
                    }
                });
                Log.e(TAG,"onPermissionGranted...");



            }

            @Override
            public void onIndividualPermissionGranted(String[] grantedPermission) {
                //某个授权
                Log.e(TAG,"onIndividualPermissionGranted() called with: grantedPermission = [" + TextUtils.join(",",grantedPermission) + "]");
            }

            @Override
            public void onPermissionDenied() {
                //某个拒绝
                Log.e(TAG,"onPermissionDenied...");
            }

            @Override
            public void onPermissionDeniedBySystem() {
                //用户选择了"不再询问"后，点击"拒绝按钮"，执行此方法
                Log.e(TAG,"onPermissionDeniedBySystem...");
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (permissionHelper != null) {
            permissionHelper.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }


    private void bindID() {
        downbtn=findViewById(R.id.web_downbtn);
        imageView=findViewById(R.id.down_img);
    }
}

//在DownTask中
public class DownTask extends AsyncTask<String,Integer,Integer> {
    private String dirPath;//下载图片的目录
    private String filePath;//下载图片的文件地址（存储位置）

    private Context context;//上下文环境
    private ImageView imageView;

    //构造方法
    public DownTask(Context context,ImageView imageView){
        this.context=context;
        this.imageView=imageView;
    }


    @Override
    protected Integer doInBackground(String... strings) {
            String fileName=strings[1];
        //判断目录是否存在，若不存在，则创建目录
        dirPath = Environment.getExternalStorageDirectory() + "/download_pics/";
        //创建目录对象
        File dir = new File(dirPath);
        if (!dir.exists()) {
            dir.mkdir();
        }

        //判断文件是否存在，若不存在，创建文件
        filePath=dirPath+fileName;//文件路径
         File file=new File(filePath);//创建文件对象
         if (file.exists()){
             return  -1;
         }
         else {
             try {
                 file.createNewFile();//不存在就创建出这个文件
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
        //创建输入流和输出流
        InputStream inputStream=null;
        OutputStream outputStream=null;

        try {
            URL url=new URL(strings[0]);
            HttpURLConnection connection= (HttpURLConnection) url.openConnection();
            //判断返回码是否正常，若正常创建输入流，否则就直接返回
            if (connection.getResponseCode()==200){
                inputStream=connection.getInputStream();
            }else {
                return -2;
            }
            outputStream=new FileOutputStream(file);
            int length=0;
            //缓冲区
            byte[] buffer=new byte[4*1024];
            while ((length=inputStream.read(buffer))!=-1){
                outputStream.write(buffer,0,length);
            }
            outputStream.flush();
            outputStream.close();
            inputStream.close();


        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return 1;
    }

    @Override
    protected void onPostExecute(Integer integer) {
        super.onPostExecute(integer);
        switch (integer){
            case 1:
                //正常下载完成
                Toast.makeText(context,"下载完成",Toast.LENGTH_SHORT).show();

                Bitmap bm= BitmapFactory.decodeFile(filePath);
                imageView.setImageBitmap(bm);
                break;
            case -1:
                //文件已存在
                Toast.makeText(context,"文件已存在",Toast.LENGTH_SHORT).show();
                break;
            case -2:
                //网络异常
                Toast.makeText(context,"网络异常",Toast.LENGTH_SHORT).show();
                break;
        }
    }
}