壁纸管理器，getCropAndSetWallpaperIntent错误

Question

我正在尝试使用getCropAndSetWallpaperIntent进行裁剪并将图像保存为墙纸。但我收到错误“Utils中的getImageUri（位图，上下文）无法应用于（位图）”。

这是代码

public void setAsWallpaper(Bitmap bitmap) {

    WallpaperManager imageView = null;
    bitmap = ((BitmapDrawable) imageView.getDrawable()).getBitmap();
    WallpaperManager wm
            = WallpaperManager.getInstance(_context);

    try {
        new Intent(wm.getCropAndSetWallpaperIntent(getImageUri(bitmap))); (**ERROR IS ON THIS LINE**)
        Toast.makeText(_context,
                _context.getString(R.string.toast_wallpaper_set),
                Toast.LENGTH_SHORT).show();
    } catch (Exception e) {
        e.printStackTrace();
        Toast.makeText(_context,
                _context.getString(R.string.toast_wallpaper_set_failed),
                Toast.LENGTH_SHORT).show();
    }
}

private Uri getImageUri(Bitmap inImage, Context inContext) {
    ByteArrayOutputStream bytes = new ByteArrayOutputStream();
    inImage.compress(Bitmap.CompressFormat.JPEG, 100, bytes);
    String path = MediaStore.Images.Media.insertImage(inContext.getContentResolver(),
            inImage, "Title", null);
    return Uri.parse(path);
}

这是logcat。

Process: com.example.wallpaper, PID: 25187

java.lang.NullPointerException: Attempt to invoke virtual method 
'android.graphics.drawable.Drawable android.app.WallpaperManager.getDrawable()' on a null object reference
                                                                                   at com.example.wallpaper.util.Utils.setAsWallpaper(Utils.java:90)
                                                                                   at com.example.wallpaper.FullScreenViewActivity.onClick(FullScreenViewActivity.java:267)
                                                                                   at android.view.View.performClick(View.java:5697)
                                                                                   at android.view.View$PerformClick.run(View.java:22526)
                                                                                   at android.os.Handler.handleCallback(Handler.java:739)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                   at android.os.Looper.loop(Looper.java:158)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:7224)
                                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

NEW ERROR LOG

E/MediaStore: Failed to insert image
                                                                           java.lang.SecurityException: Permission Denial: writing com.android.providers.media.MediaProvider uri content://media/external/images/media from pid=11235, uid=10207 requires android.permission.WRITE_EXTERNAL_STORAGE, or grantUriPermission()
                                                                               at android.os.Parcel.readException(Parcel.java:1620)
                                                                               at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:183)
                                                                               at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
                                                                               at android.content.ContentProviderProxy.insert(ContentProviderNative.java:476)
                                                                               at android.content.ContentResolver.insert(ContentResolver.java:1284)
                                                                               at android.provider.MediaStore$Images$Media.insertImage(MediaStore.java:986)
                                                                               at com.builditpossible.wallpaperpack.util.Utils.getImageUri(Utils.java:107)
                                                                               at com.builditpossible.wallpaperpack.util.Utils.setAsWallpaper(Utils.java:93)
                                                                               at com.builditpossible.wallpaperpack.FullScreenViewActivity.onClick(FullScreenViewActivity.java:259)
                                                                               at android.view.View.performClick(View.java:5697)
                                                                               at android.view.View$PerformClick.run(View.java:22526)
                                                                               at android.os.Handler.handleCallback(Handler.java:739)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                               at android.os.Looper.loop(Looper.java:158)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:7224)
                                                                               at java.lang.reflect.Method.invoke(Native Method)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

设置壁纸和下载按钮

@Override
public void onClick(View v) {
    Bitmap bitmap = ((BitmapDrawable) fullImageView.getDrawable())
            .getBitmap();
    switch (v.getId()) {
    // button Download Wallpaper tapped
    case R.id.llDownloadWallpaper:
        utils.saveImageToSDCard(bitmap);
        break;
    // button Set As Wallpaper tapped
    case R.id.llSetWallpaper:
        utils.setAsWallpaper(bitmap);
        break;
    default:
        break;
    }