简单实现打开系统相册选择一张图片并显示在UI上，适用与个人主页头像的切换。
1. 添加存储权限。AndroidManifest.xml里添加读取内存的权限。
2. 布局。布局内容比较交单，一个Button用来打开相册；一个ImageView用来接收从相册选择的图片。
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> 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"/> 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"/>
3. 动态申请权限。Google 在 Android 6.0 开始引入了权限申请机制，除了再AndroidManifest.xml里申请静态权限，还需要在代码里动态申请。
/**
* 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. 申请权限的回调。
/**
* 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. 打开相册。
/**
* 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. 结果回调。用户选择了一张图片，接收返回的结果并在ImageView里显示。、
@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();
}
}
}
}
完整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();
}
}
}
}
}
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