Android---Open the album and select pictures

Simply open the system album, select a picture and display it on the UI. It is suitable for switching with the personal homepage avatar.

1. Add storage permissions. Add permission to read memory in AndroidManifest.xml.

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

2. Layout. The layout content is relatively simple. A Button is used to open the photo album; an ImageView is used to receive the pictures selected from the photo album.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn_open_gallery"
        android:layout_width="150dp"
        android:layout_height="75dp"
        android:layout_centerHorizontal="true"
        android:text="打开相册"
        android:textSize="20sp"/>
    
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="10dp"
        android:layout_below="@+id/btn_open_gallery"/>
    
</RelativeLayout>

3. Dynamically apply for permissions. Google   introduced a permission application mechanism in Android 6.0 . In addition to applying for static permissions in AndroidManifest.xml, you also need to apply dynamically in the code.

/**
* 申请动态权限
*/
private void applyPermission() {
    //检测权限
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            // 如果没有权限，则申请需要的权限
        ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
    }else {
        // 已经申请了权限
        openGallery();
    }
}

4. Callback for requesting permission.

    /**
     * 用户选择是否开启权限操作后的回调；TODO 同意/拒绝
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 用户同样授权
                openGallery();
            }else {
                // 用户拒绝授权
                Toast.makeText(this, "你拒绝使用存储权限！", Toast.LENGTH_SHORT).show();
                Log.d("HL", "你拒绝使用存储权限！");
            }
        }
    }

5. Open the photo album.

    /**
     * 打开相册
     */
    private void openGallery() {
        Intent intent = new Intent(Intent.ACTION_PICK, null);
        intent.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI , "image/*");
        startActivityForResult(intent, OPEN_GALLERY_REQUEST_CODE);
    }

6. Result callback. The user selects an image, receives the returned result and displays it in ImageView. ,

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == OPEN_GALLERY_REQUEST_CODE) { // 检测请求码
            if (resultCode == Activity.RESULT_OK && data != null) {
                try {
                    InputStream inputStream = getContentResolver().openInputStream(data.getData());
                    Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                    // TODO 把获取到的图片放到ImageView上
                    mImg.setImageBitmap(bitmap);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
    }

Complete Demo

package com.example.opengallery;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.FileNotFoundException;
import java.io.InputStream;

public class MainActivity extends AppCompatActivity {

    private static final int PERMISSION_REQUEST_CODE = 0;
    private static final int OPEN_GALLERY_REQUEST_CODE = 1;
    private static final int TAKE_PHOTO_REQUEST_CODE = 2;

    private Button mOpenGallery;
    private ImageView mImg;

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

        mOpenGallery = findViewById(R.id.btn_open_gallery);
        mImg = findViewById(R.id.img);

        //打开相册
        mOpenGallery.setOnClickListener(v -> {
            applyPermission();
        });

    }

    /**
     * 申请动态权限
     */
    private void applyPermission() {
        //检测权限
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            // 如果没有权限，则申请需要的权限
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
        }else {
            // 已经申请了权限
            openGallery();
        }
    }

    /**
     * 用户选择是否开启权限操作后的回调；TODO 同意/拒绝
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 用户同样授权
                openGallery();
            }else {
                // 用户拒绝授权
                Toast.makeText(this, "你拒绝使用存储权限！", Toast.LENGTH_SHORT).show();
                Log.d("HL", "你拒绝使用存储权限！");
            }
        }
    }

    /**
     * 打开相册
     */
    private void openGallery() {
        Intent intent = new Intent(Intent.ACTION_PICK, null);
        intent.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI , "image/*");
        startActivityForResult(intent, OPEN_GALLERY_REQUEST_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == OPEN_GALLERY_REQUEST_CODE) { // 检测请求码
            if (resultCode == Activity.RESULT_OK && data != null) {
                try {
                    InputStream inputStream = getContentResolver().openInputStream(data.getData());
                    Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                    // TODO 把获取到的图片放到ImageView上
                    mImg.setImageBitmap(bitmap);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}