安卓4.2.2上播放视频时，安卓媒体播放器会出现闪烁问题。

Question

我在使用 Android MediaPlayer 类时遇到了一个奇怪的问题。我正使用 MediaPlayer 在 VideoView 中播放视频。这在所有设备上都可以正常工作，但在搭载 Android 4.2.2 的三星 GT-I8200N 上却无法正常播放。其实我听说某些三星 4.1.X 设备无法播放视频，但我并没有能够获取到这些设备。在 Google Android 模拟器中没有出现任何错误。

更多细节：搭载 Android 4.2.2 的三星GT-I8200N 能够在一个片段中播放视频，但在另一个片段中却不能，尽管使用的是同样的代码来播放视频。当视频开始播放时，整个屏幕会闪烁黑色，只有视频应该呈现的空间不受影响。

以下是代码：

public abstract class AbstractSignVideoFragment extends Fragment {

private static final double MAXMIMUM_VIDEO_HEIGHT_ON_LANDSCAPE = 0.4;
private static final double MAXIMUM_VIDEO_WIDTH_ON_PORTRAIT = 0.8;
private final static String TAG = AbstractSignVideoFragment.class.getSimpleName();
private static final String ANDROID_RESOURCE = "android.resource://";
private static final String SLASH = "/";
private static final String RAW = "raw";
protected VideoView videoView;
protected ProgressBar progressBar;

@SuppressWarnings("BooleanMethodIsAlwaysInverted")
protected boolean isSetupVideoViewSuccessful(final Sign sign, final SOUND sound, final CONTROLS controls) {
    initializeMediaController();
    final String mainActivityPackageName = getActivity().getPackageName();
    final int signIdentifier = getActivity().getResources().getIdentifier(sign.getName(), RAW, mainActivityPackageName);
    if (0 == signIdentifier) {
        return false;
    }
    final Uri uri = Uri.parse(ANDROID_RESOURCE + mainActivityPackageName + SLASH + signIdentifier);
    if (!isVideoViewDimensionSetToMatchVideoMetadata(this.videoView, uri)) {
        return false;
    }
    this.videoView.setVideoURI(uri);
    this.videoView.requestFocus();
    this.videoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
        public void onPrepared(MediaPlayer mp) {
            AbstractSignVideoFragment.this.progressBar.setVisibility(View.GONE);
            if (sound.equals(SOUND.OFF)) {
                mp.setVolume(0f, 0f);
            }
            AbstractSignVideoFragment.this.videoView.start();
            AbstractSignVideoFragment.this.videoView.setContentDescription(getActivity()
                    .getString(R.string.videoIsPlaying) + ": " + sign.getName());
            Log.d(TAG, String.format("Actual width: %s, Actual height: %s",
                    AbstractSignVideoFragment.this.videoView.getWidth(),
                    AbstractSignVideoFragment.this.videoView.getHeight()));
            // Set the MediaController to null so the controls are not 'popping up'
            // when the video plays for the first time.
            AbstractSignVideoFragment.this.videoView.setMediaController(null);
        }
    });
    this.videoView.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
        @Override
        public void onCompletion(MediaPlayer mp) {
            if (controls.equals(CONTROLS.SHOW)) {
                initializeMediaController();
            }
        }
    });
    return true;
}

private void initializeMediaController() {
    final MediaController mediaController = new MediaController(getActivity(), false);
    mediaController.setAnchorView(this.videoView);
    this.videoView.setMediaController(mediaController);
}

private boolean isVideoViewDimensionSetToMatchVideoMetadata(VideoView videoView, Uri uri) {
    String metadataVideoWidth;
    String metadataVideoHeight;
    try {
        final MediaMetadataRetriever metaRetriever = new MediaMetadataRetriever();
        metaRetriever.setDataSource(getActivity(), uri);
        metadataVideoWidth = metaRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_WIDTH);
        metadataVideoHeight = metaRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_HEIGHT);
        metaRetriever.release();
        Validate.notEmpty(metadataVideoWidth);
        Validate.notEmpty(metadataVideoHeight);
    } catch (NullPointerException | IllegalArgumentException ex) {
        return false;
    }
    final double videoWidth = Double.valueOf(metadataVideoWidth);
    final double videoHeight = Double.valueOf(metadataVideoHeight);
    final double videoRatio = videoWidth / videoHeight;
    Log.d(TAG, String.format("videoWidth: %s, videoHeight: %s, videoRatio: %s", videoWidth, videoHeight, videoRatio));
    boolean isOrientationPortrait = Configuration.ORIENTATION_PORTRAIT == getResources().getConfiguration().orientation;
    int displayHeight = getResources().getDisplayMetrics().heightPixels;
    int displayWidth = getResources().getDisplayMetrics().widthPixels;
    Log.d(TAG, String.format("displayHeight: %s, displayWidth: %s", displayHeight, displayWidth));
    final double desiredVideoWidth, desiredVideoHeight;
    if (isOrientationPortrait) {
        desiredVideoWidth = displayWidth * MAXIMUM_VIDEO_WIDTH_ON_PORTRAIT;
        desiredVideoHeight = 1 / (videoRatio / desiredVideoWidth);
        Log.d(TAG, String.format("OrientationPortrait: desiredVideoWidth: %s, desiredVideoHeight: %s", desiredVideoWidth, desiredVideoHeight));
    } else { // orientation is Landscape
        desiredVideoHeight = displayHeight * MAXMIMUM_VIDEO_HEIGHT_ON_LANDSCAPE;
        desiredVideoWidth = desiredVideoHeight * videoRatio;
        Log.d(TAG, String.format("OrientationLandscape: desiredVideoWidth: %s, desiredVideoHeight: %s", desiredVideoWidth, desiredVideoHeight));
    }
    final ViewGroup.LayoutParams layoutParams = videoView.getLayoutParams();
    layoutParams.width = (int) desiredVideoWidth;
    layoutParams.height = (int) desiredVideoHeight;
    return true;
}

public enum SOUND {ON, OFF}

public enum CONTROLS {SHOW, HIDE}
}

以下是当屏幕闪烁时循环的logcat输出：

D/v_gal(115): [tid=275] gcmVERIFY_ARGUMENT 失败： D/v_gal(115): [tid=275] gcmONERROR: status=-1(gcvSTATUS_INVALID_ARGUMENT) @ _Blit(2208) E/v_hwc(115): _Blit 失败：status=-1 D/v_gal(115): [tid=275] gcmONERROR: status=-1(gcvSTATUS_INVALID_ARGUMENT) @ hwcComposeG2D(615) E/v_hwc(115): hwcComposeG2D 失败：status=-1 E/v_hwc(115): _Set(1007)：合成失败

完整的logcat输出可以在此处找到：Github问题（完整的logcat） 视频视图代码：

< VideoView
android:id="@+id/signTrainerVideoView"
android:layout_width="0dip"
android:layout_height="0dip"
android:layout_below="@+id/signTrainerQuestionText"
android:layout_centerHorizontal="true" />

该片段的完整布局xml可以在此处找到：布局xml（完整片段）

- Matthias T

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嗯...VideoView是一个非常老的小部件。你试过用TextureView吗？看看这个链接。 - Mimmo Grottoli

这个问题有没有解决方案？ - Rajesh

Answer 1

我不确定这是否能解决问题，但我会报告其中看似可以改进的部分。

为了实现您的VideoView大小：

final ViewGroup.LayoutParams layoutParams = videoView.getLayoutParams();
layoutParams.width = (int) desiredVideoWidth;
layoutParams.height = (int) desiredVideoHeight;
videoView.setLayoutParams(layoutParams); // Input Changes
videoView.getHolder().setSizeFromLayout(); // Apply Changes

根据我的实验，“0dip”大小意味着使用权重参数进行计算，而您似乎没有提供该参数。可能是错误的，但值得一提。

// Add android:weightSum="1" to the sup. Layout
// And set a weight there
<VideoView
            android:id="@+id/signTrainerVideoView"
            android:layout_width="0dip"
            android:layout_height="0dip"
            android:layout_weight="1"
            android:layout_below="@+id/signTrainerQuestionText"
            android:layout_centerHorizontal="true" />

- J.Jacobs

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谢谢回复。我会尽快检查它。 - Matthias T