UPDATE（24/10/19）：我稍微修改了问题的语言。拒绝投票的人，如果仍然不清楚，请通过评论让我公开知道，以便我进一步完善（我只是在闭幕投票中说不清楚，mod名称或原因都没有）。请知道英语不是我的母语，我真的很需要帮助。
所以我想这与Java基础知识和OOP更为相关，但是我已经看到了一些常见的Android类所遵循的模式。 Google经常不推荐使用旧功能，而是使用更好的功能，而我正在考虑使用自定义视图执行类似的操作。
我想在android中构建一个易于创建的视频播放器，并应在多个事件上返回回调。为此，我希望用户使用我的功能而不是内置视频视图的功能。因此，我正在应用几种方法来防止用户使用这些内置函数：
@Deprecated表示法来显示函数名称，例如getVolume() @Override @deprecated
public void getWidth(){
throw new UnsupportedOperationException("useMyVideoPlayer#getVideoWidth()");
}
init()或它们各自的替代方案中实现这些功能。这是代码（检查代码行上的注释：super.setOnErrorListener(errorListener);）
public class MyVideoPlayer extends VideoView {
public static final String TAG = "MyVP>>";
private MyPlayerCurrentPlaybackState currentPlaybackState;
private MediaController mediaController;
@Nullable
private MyVideoPlayerListener playerListener;
public MyVideoPlayer(Context context) {
super(context);
init();
}
public MyVideoPlayer(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public MyVideoPlayer(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
public MyVideoPlayer(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init();
}
public void init() {
currentPlaybackState = MyPlayerCurrentPlaybackState.STOPPED;
mediaController = new MediaController(this.getContext());
mediaController.setAnchorView(this);
MediaPlayer.OnCompletionListener onCompletionListener = new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mp) {
Log.e(TAG, "internalListener:onCompletion: called");
mp.reset();
mp.setDisplay(MyVideoPlayer.this.getHolder());
currentPlaybackState = MyPlayerCurrentPlaybackState.STOPPED;
if (playerListener != null) {
playerListener.onCompleted(mp);
} else {
Log.e(TAG, "onCompletionListener:onCompletion: playerListener is null");
}
}
};
super.setOnCompletionListener(onCompletionListener);
MediaPlayer.OnErrorListener errorListener = new MediaPlayer.OnErrorListener() {
@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
currentPlaybackState = MyPlayerCurrentPlaybackState.STOPPED;
if (playerListener != null) {
playerListener.onError(what, extra);
} else {
Log.e(TAG, "errorListener:onError: playerListener is null");
}
return true;// indicates we handled error
}
};
super.setOnErrorListener(errorListener);// <---setting error listener *inside* the view only and making setOnErrorListener(...) deprecated so that user won't use it
MediaPlayer.OnPreparedListener preparedListener = new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
//play(); // or should we call mp.start?
if (playerListener != null) {
playerListener.onPlayerPrepared(MyVideoPlayer.this);
} else {
Log.e(TAG, "preparedListener:onPrepared: player listener is null");
}
}
};
super.setOnPreparedListener(preparedListener);
}
@Nullable
public MyVideoPlayerListener getMyPlayerListener() {
return playerListener;
}
public void setMyPlayerListener(@NonNull MyVideoPlayerListener playerListener) {
this.playerListener = playerListener;
}
//---------following methods throw exception, do not use-----vvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
@Override @Deprecated
public void setOnCompletionListener(@Nullable MediaPlayer.OnCompletionListener implementorsListener) {
//update: user is now not adding the on completion listener at all. he/she will only use our methods now.
throw new UnsupportedOperationException("Use MyVideoPlayer#setMyPlayerListener(...) ");
}
@Override @Deprecated
public void setOnErrorListener(MediaPlayer.OnErrorListener implementorsListener) {
//update: user is now not adding the on completion listener at all. he/she will only use our methods now.
throw new UnsupportedOperationException("Use MyVideoPlayer#setMyPlayerListener(...) ");
}
@Override @Deprecated
public int getDuration() {
throw new UnsupportedOperationException("Use MyVideoPlayer#gettotalDuration(...) ");
}
@Deprecated
public void start() {
// did because it doesn't look cool
throw new UnsupportedOperationException("Use MyVideoPlayer#play() ");
}
@Override @Deprecated
public void stopPlayback() {
// did because it doesn't look cool
throw new UnsupportedOperationException("Use MyVideoPlayer#stop() ");
}
//----------------------------------------------------------------------------------------------
@Override @Deprecated
public void setOnPreparedListener(MediaPlayer.OnPreparedListener implementorsListener) {
throw new UnsupportedOperationException("use MyVideoPlayer#onPlayerPrepared()");
}
public void play() {
super.start();
if (playerListener != null) {
playerListener.onPlay();
} else {
Log.e(TAG, "play: player listener is null");
}
currentPlaybackState = MyPlayerCurrentPlaybackState.PLAYING;
}
@Override
public void pause() {
// didn't throwed any exception because its already cool
super.pause();
currentPlaybackState = MyPlayerCurrentPlaybackState.PAUSED;
if (playerListener != null) {
playerListener.onPause();
} else {
Log.e(TAG, "play: player listener is null");
}
}
@Override
public void resume() {
// didn't throwed any exception because its already cool
super.start();
if (playerListener != null) {
playerListener.onResume();
} else {
Log.e(TAG, "play: player listener is null");
}
currentPlaybackState = MyPlayerCurrentPlaybackState.PLAYING;
}
public void stop() {
if (currentPlaybackState != MyPlayerCurrentPlaybackState.STOPPED) {
super.stopPlayback();
if (playerListener != null) {
playerListener.onStop();
} else {
Log.e(TAG, "play: player listener is null");
}
currentPlaybackState = MyPlayerCurrentPlaybackState.STOPPED;
}
}
public int gettotalDuration() {
return currentPlaybackState ==
MyPlayerCurrentPlaybackState.STOPPED ? 0 : super.getDuration();
}
//returns current video volume in range 0-100
public int getVolume() {
// Get the system's audio service and get media volume from it.
AudioManager audioManager =
(AudioManager) getContext().getSystemService(Context.AUDIO_SERVICE);
if (audioManager != null) {
double volume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
double max = audioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
if (max <= 0) {
return 0;
}
// Return a range from 0-100.
return (int) ((volume / max) * 100.0f);
}
return 0;
}
public enum MyPlayerCurrentPlaybackState {
STOPPED, PAUSED, PLAYING
}
public interface MyVideoPlayerListener {
void onPlay();
void onPause();
void onResume();
void onCompleted(MediaPlayer mp);
void onError( int what, int extra);
void onPlayerPrepared(MyVideoPlayer myVideoPlayer);
void onStop();
}
/* must implement features
public interface VideoPlayer {
void play();
void pause();
void resume();
int getCurrentPosition();
void seekTo(int videoPosition);
int getDuration();
int getVolume();
void stopPlayback();
void disablePlaybackControls();
void enablePlaybackControls();
void setVideoPath(String videoUrl);
void addPlayerCallback(PlayerCallback callback);
void removePlayerCallback(PlayerCallback callback);
}
*
* */
}
我希望上面的示例表明我的意图：我希望用户不使用内置于start()，setOnErrorListener(...)等方法中，但是该库可以处理那些函数本身（并给用户回调）或定义了我希望用户使用的其他一些函数，而不是内置函数（例如，我希望用户调用自定义视图的play()函数，而不是已经存在的函数start()函数通过inheritance.来自父级
但是当我通过这些行调用代码时：
MyVideoPlayer mvp = findViewById(R.id.mvp_main);
mvp.setVideoURI(Uri.parse(MyTags.CONTENT_URL));
mvp.setMyPlayerListener(new MyVideoPlayer.MyVideoPlayerListener() {
@Override
public void onPlay() {
Log.e(TAG, "onPlay: Video is now playing" );
}
@Override
public void onPause() {
Log.e(TAG, "onPause: Video Paused" );
}
@Override
public void onResume() {
Log.e(TAG, "onResume: video resumed" );
}
@Override
public void onCompleted(MediaPlayer mp) {
Log.e(TAG, "onCompleted: video playback completed" );
}
@Override
public void onError(int what, int extra) {
Log.e(TAG, "onError: error happenned: what:"+what+",extra:"+extra );
}
@Override
public void onPlayerPrepared(MyVideoPlayer myVideoPlayer) {
Log.e(TAG, "onPlayerPrepared: video is prepared,plau video" );
myVideoPlayer.play();
}
@Override
public void onStop() {
Log.e(TAG, "onStop: media playback stopped" );
}
});
ie，即当用户在其应用程序中使用我的库时，如果调用诸如mvp.play()这样的库定义函数，例如java.lang.UnsupportedOperationException: Use MyVideoPlayer#play()，则表示正在调用我覆盖的start()函数，这将引发异常而不是super.start()。为什么？另外，我是在正确使用@Deprecated批注（仅仅是为了显示删除线警告）还是该批注也进行了一些不需要的更改？
答案 0 :(得分：2)
您可以应用代理/装饰图案：
编写您自己的Videoplayer，以实现和扩展原始Vidoeview实现的类。 这是一个伪代码，可以给您一个提示：
//extends and implements the same interface and parent as the VideoView did, o that they will have the same methods to work properly.
public class MyVideoViewer extends SurfaceView implements
MediaController.MediaPlayerControl{
//private modifier to prevent others from directly calling the system's player
private VideoView view;
//you can just delete start method, so users using your player cannot even see this method.
/**void start(){
}*/
public void init(){
// do your things. can necessary method from videoplayer
view.setOnCompletionListener(listener) etc.
}
public void play()
{
view.start();
}
//indirectly call all necessary methods to make sure the system's player work properly.
@override
public void draw(arg1,arg2){
view.draw(arg1,arg2);
}
}
这样做，您的播放器仅公开您想要其公开的方法，将所有不必要的方法隐藏在用户后面。仍然可以正常工作，因为在下面，有一个适合您的播放器的适当的Videoview系统。