我们做二级采样的时候最好用到一个工具类工具类在下一遍一些简单易懂的代码可参考-优快云博客

本文介绍了一个Android应用中实现图片选择、二次采样和质量压缩的方法。通过使用Intent.ACTION_PICK选择图片，然后利用自定义的ImageUtil类进行图片尺寸调整和质量压缩，最终在ImageView中显示处理后的图片。

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public class MainActivity extends AppCompatActivity {

private EditText width;//宽
private EditText height;//高
private EditText quality;//质量

private Button getImage;//获取图片
private Button show;//显示图片
private ImageView image;

private final int PICK_IMAGE = 100;
private Uri uri;

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

    //Bitmap bitmpa;

    //bitmpa.compress(Bitmap.CompressFormat.JPEG, 70, );

    width = findViewById(R.id.width);
    height = findViewById(R.id.height);
    quality = findViewById(R.id.quality);

    getImage = findViewById(R.id.get_image);
    show = findViewById(R.id.show);

    image = findViewById(R.id.image);

    getImage.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(Intent.ACTION_PICK);
            intent.setType("image/*");
            startActivityForResult(intent, PICK_IMAGE);
        }
    });


    show.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String filePath = getRealPathFromURI(uri);

            //二次采样
            Log.i("TEST",filePath);
            Bitmap bitmap = ImageUtil.scaleBitmap(filePath, Integer.parseInt(width.getText().toString()), Integer.parseInt(height.getText().toString()));

            bitmap = ImageUtil.compress(bitmap, Integer.parseInt(quality.getText().toString()), new File(Environment.getExternalStorageDirectory(), "tmp2.jpg"));
            image.setImageBitmap(bitmap);
            //BitmapFactory.de
            //质量压缩

            //展示
        }
    });
}

private String getRealPathFromURI(Uri contentUri) { //传入图片uri地址
    String[] proj = { MediaStore.Images.Media.DATA };
    CursorLoader loader = new CursorLoader(this, contentUri, proj, null, null, null);
    Cursor cursor = loader.loadInBackground();
    int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
    cursor.moveToFirst();
    return cursor.getString(column_index);
}


@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    if(requestCode == PICK_IMAGE) {
        if(resultCode == RESULT_OK) {
            //图片uri
            uri = data.getData();
        }
        return;
    }
    super.onActivityResult(requestCode, resultCode, data);
}

}