我是Android编程的新手，作为学习的一部分，我试图运行这个开源项目（下面），最终导致import com.example.android.apis.R;的错误。还有R的地方和所有地方。据我所知R.java是自动生成的，我们不需要创建或编辑它。这个错误的原因是什么？任何人都可以解释一下。我用Eclipse来运行这个项目。
package com.example.android.apis.media;
import com.example.android.apis.R;
import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnBufferingUpdateListener;
import android.media.MediaPlayer.OnCompletionListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.media.MediaPlayer.OnVideoSizeChangedListener;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
public class MediaPlayerDemo_Video extends Activity implements
OnBufferingUpdateListener, OnCompletionListener,
OnPreparedListener, OnVideoSizeChangedListener, SurfaceHolder.Callback {
private static final String TAG = "MediaPlayerDemo";
private int mVideoWidth;
private int mVideoHeight;
private MediaPlayer mMediaPlayer;
private SurfaceView mPreview;
private SurfaceHolder holder;
private String path;
private Bundle extras;
private static final String MEDIA = "media";
private static final int LOCAL_AUDIO = 1;
private static final int STREAM_AUDIO = 2;
private static final int RESOURCES_AUDIO = 3;
private static final int LOCAL_VIDEO = 4;
private static final int STREAM_VIDEO = 5;
private boolean mIsVideoSizeKnown = false;
private boolean mIsVideoReadyToBePlayed = false;
/**
*
* Called when the activity is first created.
*/
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.mediaplayer_2);
mPreview = (SurfaceView) findViewById(R.id.surface);
holder = mPreview.getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
extras = getIntent().getExtras();
}
private void playVideo(Integer Media) {
doCleanUp();
try {
switch (Media) {
case LOCAL_VIDEO:
/*
* TODO: Set the path variable to a local media file path.
*/
path = "";
if (path == "") {
// Tell the user to provide a media file URL.
Toast
.makeText(
MediaPlayerDemo_Video.this,
"Please edit
MediaPlayerDemo_Video Activity, "
+ "and set the path
variable to your media file path."
+ " Your media file
must be stored on sdcard.",
Toast.LENGTH_LONG).show();
}
break;
case STREAM_VIDEO:
/*
* TODO: Set path variable to progressive streamable mp4 or
* 3gpp format URL. Http protocol should be used.
* Mediaplayer can only play "progressive streamable
* contents" which basically means: 1. the movie atom has to
* precede all the media data atoms. 2. The clip has to be
* reasonably interleaved.
*
*/
path = "";
if (path == "") {
// Tell the user to provide a media file URL.
Toast
.makeText(
MediaPlayerDemo_Video.this,
"Please edit
MediaPlayerDemo_Video Activity,"
+ " and set the path
variable to your media file URL.",
Toast.LENGTH_LONG).show();
}
break;
}
// Create a new media player and set the listeners
mMediaPlayer = new MediaPlayer();
mMediaPlayer.setDataSource(path);
mMediaPlayer.setDisplay(holder);
mMediaPlayer.prepare();
mMediaPlayer.setOnBufferingUpdateListener(this);
mMediaPlayer.setOnCompletionListener(this);
mMediaPlayer.setOnPreparedListener(this);
mMediaPlayer.setOnVideoSizeChangedListener(this);
mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
} catch (Exception e) {
Log.e(TAG, "error: " + e.getMessage(), e);
}
}
public void onBufferingUpdate(MediaPlayer arg0, int percent) {
Log.d(TAG, "onBufferingUpdate percent:" + percent);
}
public void onCompletion(MediaPlayer arg0) {
Log.d(TAG, "onCompletion called");
}
public void onVideoSizeChanged(MediaPlayer mp, int width, int height) {
Log.v(TAG, "onVideoSizeChanged called");
if (width == 0 || height == 0) {
Log.e(TAG, "invalid video width(" + width + ") or height("
+ height + ")");
return;
}
mIsVideoSizeKnown = true;
mVideoWidth = width;
mVideoHeight = height;
if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) {
startVideoPlayback();
}
}
public void onPrepared(MediaPlayer mediaplayer) {
Log.d(TAG, "onPrepared called");
mIsVideoReadyToBePlayed = true;
if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) {
startVideoPlayback();
}
}
public void surfaceChanged(SurfaceHolder surfaceholder, int i, int
j, int k) {
Log.d(TAG, "surfaceChanged called");
}
public void surfaceDestroyed(SurfaceHolder surfaceholder) {
Log.d(TAG, "surfaceDestroyed called");
}
public void surfaceCreated(SurfaceHolder holder) {
Log.d(TAG, "surfaceCreated called");
playVideo(extras.getInt(MEDIA));
}
@Override
protected void onPause() {
super.onPause();
releaseMediaPlayer();
doCleanUp();
}
@Override
protected void onDestroy() {
super.onDestroy();
releaseMediaPlayer();
doCleanUp();
}
private void releaseMediaPlayer() {
if (mMediaPlayer != null) {
mMediaPlayer.release();
mMediaPlayer = null;
}
}
private void doCleanUp() {
mVideoWidth = 0;
mVideoHeight = 0;
mIsVideoReadyToBePlayed = false;
mIsVideoSizeKnown = false;
}
private void startVideoPlayback() {
Log.v(TAG, "startVideoPlayback");
holder.setFixedSize(mVideoWidth, mVideoHeight);
mMediaPlayer.start();
}
}
这是我试图运行的代码。
答案 0 :(得分：3)
我通过在项目属性 / * Android *中将项目构建目标从Android 1.6更改为Android 4.2来解决此问题。
旧版本不支持布局xml文件中的某些新语法，但这些错误信息不会显示在源代码中，而是显示在输出窗口中。
答案 1 :(得分：0)
这可能有几个原因。
确保您的所有文件中没有任何XML错误。当您遇到XML错误时，将不会构建R.文件 。修复错误后，应自动构建R.文件。如果没有，请尝试清理您的项目。
另外，请确保您没有此行：
import android.R;
在你班上。
答案 2 :(得分：0)
这意味着布局或清单文件（XML）上的错误。
我认为常见的错误可能是布局设计错误，缺少标签等等
请先修复它们并再次清理项目