Android开发实现从相册中选择照片功能详解

imageView01.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
    if(ContextCompat.checkSelfPermission(MainActivity.this,
        Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
      ActivityCompat.requestPermissions(MainActivity.this,new String[]{
          Manifest.permission.WRITE_EXTERNAL_STORAGE
      },1);
    }
    Intent intent = new Intent(Intent.ACTION_PICK,
        android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    startActivityForResult(intent, IMAGE_REQUEST_CODE);
  }
});

@TargetApi(19)
private void handleImageOmKitKat(Intent data){
    String imagePath = null;
    Uri uri = data.getData();
    if (DocumentsContract.isDocumentUri(this,uri)){
      //如果document类型是U日，则通过document id处理
      String docId = DocumentsContract.getDocumentId(uri);
      if ("com.android.providers.media.documents".equals(uri.getAuthority())){
        String id = docId.split(":")[1];//解析出数字格式id
        String selection = MediaStore.Images.Media._ID + "=" + id;
        imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,selection);
      }else if ("com.android.providers.downloads.documents".equals(uri.getAuthority())){
        Uri cOntentUri= ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),Long.valueOf(docId));
        imagePath = getImagePath(contentUri,null);
      }
    }else if ("content".equalsIgnoreCase(uri.getScheme())){
      //如果是普通类型 用普通方法处理
      imagePath = getImagePath(uri,null);
    }else if ("file".equalsIgnoreCase(uri.getScheme())){
      //如果file类型位uri直街获取图片路径即可
      imagePath = uri.getPath();
    }
    displayImage(imagePath);
}

/*定义一个Handler，定义延时执行的行为*/
public void chnage(){
  new Thread(){
    @Override
    public void run() {
      while ( bitmap == null ){
        bitmap = BitmapFactory.decodeFile(path);
        Log.v("qwe","123");
      }
      Message message = handler.obtainMessage();
      message.obj = 0;
      handler.sendMessage(message);
    }
  }.start();
}

private void handleImageBeforeKitKat(Intent data){
    Uri uri = data.getData();
    String imagePath = getImagePath(uri,null);
    displayImage(imagePath);
}
private String getImagePath(Uri uri, String selection){
    String path = null;
    //通过Uri和selection来获取真实图片路径
    Cursor cursor = getContentResolver().query(uri, null, selection, null, null);
    if (cursor != null){
      if (cursor.moveToFirst()){
        path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
      }
      cursor.close();
    }
    return path;
}
private void displayImage(String imagePath){
    if (imagePath != null){
      Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
      imageView01.setImageBitmap(bitmap);
    }else {
      Toast.makeText(MainActivity.this,"fail to get image",Toast.LENGTH_SHORT).show();
    }
}

//从相册获得图片
Bitmap bitmap;
//判断返回到的Activity
private static final int IMAGE_REQUEST_CODE = 0;
//图片路径
private String path ;
private Handler handler = new Handler(){
  @Override
  public void handleMessage(Message msg) {
    if((Integer)msg.obj==0){
      imageView01.setImageBitmap(bitmap);
    }
    super.handleMessage(msg);
  }
};