如何获得android锁屏壁纸？

Question

我使用下面的代码检索android 8.1手机上的android锁屏壁纸:

WallpaperManager manager = WallpaperManager.getInstance(getActivity());
ParcelFileDescriptor pfd = manager.getWallpaperFile(WallpaperManager.FLAG_LOCK);
if (pfd == null) // pfd is always null for FLAG_LOCK, why?
    return;
Bitmap lockScreenWallpaper = BitmapFactory.decodeFileDescriptor(pfd.getFileDescriptor());
// ...

我已经授予了READ_EXTERNAL_STORAGE许可并预先设置了锁屏壁纸.

我在真正的手机上运行演示,发现pfd它总是为空FLAG_LOCK,所以我无法获得锁屏壁纸.请帮忙解决问题,谢谢.

Answer 1

我正在测试的代码与您的相似。我已经在三星 A5 和 LG Nexus 5X 上对其进行了测试。

主活动.java

import android.Manifest;
import android.annotation.SuppressLint;
import android.app.WallpaperManager;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Build;
import android.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    public static final int REQUEST_CODE_EXTERNAL_STORAGE = 5;

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

        String permission = Manifest.permission.WRITE_EXTERNAL_STORAGE;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            permission = Manifest.permission.READ_EXTERNAL_STORAGE;
        }

        if (ContextCompat.checkSelfPermission(this, permission) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{permission}, REQUEST_CODE_EXTERNAL_STORAGE);
        } else {
            retrieveLockScreenWallpaper();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case REQUEST_CODE_EXTERNAL_STORAGE: {
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    retrieveLockScreenWallpaper();
                }
            }
        }
    }

    @SuppressLint("MissingPermission")
    private void retrieveLockScreenWallpaper() {
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
            WallpaperManager manager = WallpaperManager.getInstance(getApplicationContext());
            ParcelFileDescriptor descriptor = manager.getWallpaperFile(WallpaperManager.FLAG_LOCK);
            if (descriptor != null) {
                Bitmap bitmap = BitmapFactory.decodeFileDescriptor(descriptor.getFileDescriptor());
                ((ImageView) findViewById(R.id.imageView)).setImageBitmap(bitmap);
            }
        }
    }

}

清单文件

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="aminography.com.lockscreenapplication">

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

    <application

        ...

    </application>

</manifest>

.

LGE Nexus 5X（Android 8.1.0，API 27）上的结果：

Answer 2

我自己找到了答案,我希望它能帮助其他人解决同样的问题.

getWallpaperFile的官方文档说:If no lock-specific wallpaper has been configured for the given user, then this method will return null when requesting FLAG_LOCK rather than returning the system wallpaper's image file.

描述含糊不清,至少不够清楚,这是什么意思？如果将照片设置为锁定屏幕和主屏幕壁纸,则两者共享同一文件,然后通过调用

ParcelFileDescriptor pfd = wallpaperManager.getWallpaperFile(WallpaperManager.FLAG_LOCK);

pfd 将永远为null,那么你应该这样得到锁屏壁纸:

if (pfd == null)
    pfd = wallpaperManager.getWallpaperFile(WallpaperManager.FLAG_SYSTEM);

你会得到非null pfd.情况就是这样no lock-specific wallpaper has been configured.

相反,lock-specific wallpaper has been configured如果直接wallpaperManager.getWallpaperFile(WallpaperManager.FLAG_SYSTEM)将照片设置为锁屏壁纸,则会返回非空值.

所以这是我用来检索锁屏壁纸的代码:

/**
 * please check permission outside
 * @return Bitmap or Drawable
 */
public static Object getLockScreenWallpaper(Context context)
{
    WallpaperManager wallpaperManager = WallpaperManager.getInstance(context);
    if (Build.VERSION.SDK_INT >= 24)
    {
        ParcelFileDescriptor pfd = wallpaperManager.getWallpaperFile(WallpaperManager.FLAG_LOCK);
        if (pfd == null)
            pfd = wallpaperManager.getWallpaperFile(WallpaperManager.FLAG_SYSTEM);
        if (pfd != null)
        {
            final Bitmap result = BitmapFactory.decodeFileDescriptor(pfd.getFileDescriptor());

            try
            {
                pfd.close();
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }

            return result;
        }
    }
    return wallpaperManager.getDrawable();
}

不要忘记添加READ_EXTERNAL_STORAGE清单文件并将其授予外部.