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我不確定爲什麼，但是當我嘗試導入這個項目時，我最終無法在編輯項目之前將R解析爲變量錯誤。我發現很難相信作者會發佈一個不能編譯的源代碼示例 - 這可能是我在使用eclipse時可能會遇到的問題嗎？從教程源項目導入項目結果R無法解析爲變量
http://alucard1990.hubpages.com/hub/How-to-Make-a-Simple-Media-Player-for-Android
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 298 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 302 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 287 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 294 Java Problem
error: No resource identifier found for attribute 'onClick' in package 'android' main.xml /MyMediaPlayer/res/layout line 15 Android AAPT Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 307 Java Problem
error: No resource identifier found for attribute 'onClick' in package 'android' main.xml /MyMediaPlayer/res/layout line 19 Android AAPT Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 312 Java Problem
error: No resource identifier found for attribute 'onClick' in package 'android' main.xml /MyMediaPlayer/res/layout line 23 Android AAPT Problem
DIRECTORY_PICTURES cannot be resolved or is not a field MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 118 Java Problem
DIRECTORY_MUSIC cannot be resolved or is not a field MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 117 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 90 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 284 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 281 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 278 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 253 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 89 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 88 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 74 Java Problem
R cannot be resolved to a variable MyMediaPlayerActivity.java /MyMediaPlayer/src/com/technegames/mymediaplayer line 55 Java Problem
來源：
public class MyMediaPlayerActivity extends Activity {
WakeLock wakeLock;
private static final String[] EXTENSIONS = { ".mp3", ".mid", ".wav", ".ogg", ".mp4" }; //Playable Extensions
List<String> trackNames; //Playable Track Titles
List<String> trackArtworks; //Track artwork names
AssetManager assets; //Assets (Compiled with APK)
File path; //directory where music is loaded from on SD Card
File path2; //directory where album artwork is loaded from on SD Card
Music track; //currently loaded track
ImageView bg; //Track artwork
Button btnPlay; //The play button will need to change from 'play' to 'pause', so we need an instance of it
Random random; //used for shuffle
boolean shuffle; //is shuffle mode on?
boolean isTuning; //is user currently jammin out, if so automatically start playing the next track
int currentTrack; //index of current track selected
int type; //0 for loading from assets, 1 for loading from SD card
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setVolumeControlStream(AudioManager.STREAM_MUSIC);
PowerManager powerManager = (PowerManager) getSystemService(Context.POWER_SERVICE);
wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, "Lexiconda");
setContentView(R.layout.main);
initialize(0);
}
@Override
public void onResume(){
super.onResume();
wakeLock.acquire();
}
@Override
public void onPause(){
super.onPause();
wakeLock.release();
if(track != null){
if(track.isPlaying()){
track.pause();
isTuning = false;
btnPlay.setBackgroundResource(R.drawable.play);
}
if(isFinishing()){
track.dispose();
finish();
}
} else{
if(isFinishing()){
finish();
}
}
}
private void initialize(int type){
bg = (ImageView) findViewById(R.id.bg);
btnPlay = (Button) findViewById(R.id.btnPlay);
btnPlay.setBackgroundResource(R.drawable.play);
trackNames = new ArrayList<String>();
trackArtworks = new ArrayList<String>();
assets = getAssets();
currentTrack = 0;
shuffle = false;
isTuning = false;
random = new Random();
this.type = type;
addTracks(getTracks());
loadTrack();
}
//Generate a String Array that represents all of the files found
private String[] getTracks(){
if(type == 0){
try {
String[] temp = getAssets().list("");
return temp;
} catch (IOException e) {
e.printStackTrace();
Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_LONG).show();
}
} else if(type == 1){
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)
|| Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED_READ_ONLY)){
path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC);
path2 = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
String[] temp = path.list();
return temp;
} else{
Toast.makeText(getBaseContext(), "SD Card is either mounted elsewhere or is unusable", Toast.LENGTH_LONG).show();
}
}
return null;
}
//Adds the playable files to the trackNames List
private void addTracks(String[] temp){
if(temp != null){
for(int i = 0; i < temp.length; i++){
//Only accept files that have one of the extensions in the EXTENSIONS array
if(trackChecker(temp[i])){
trackNames.add(temp[i]);
trackArtworks.add(temp[i].substring(0, temp[i].length()-4));
}
}
Toast.makeText(getBaseContext(), "Loaded " + Integer.toString(trackNames.size()) + " Tracks", Toast.LENGTH_SHORT).show();
}
}
//Checks to make sure that the track to be loaded has a correct extenson
private boolean trackChecker(String trackToTest){
for(int j = 0; j < EXTENSIONS.length; j++){
if(trackToTest.contains(EXTENSIONS[j])){
return true;
}
}
return false;
}
//Loads the track by calling loadMusic
private void loadTrack(){
if(track != null){
track.dispose();
}
if(trackNames.size() > 0){
track = loadMusic(type);
setImage("drawable/" + trackArtworks.get(currentTrack));
}
}
//loads a Music instance using either a built in asset or an external resource
private Music loadMusic(int type){
switch(type){
case 0:
try{
AssetFileDescriptor assetDescriptor = assets.openFd(trackNames.get(currentTrack));
return new Music(assetDescriptor);
} catch(IOException e){
e.printStackTrace();
Toast.makeText(getBaseContext(), "Error Loading " + trackNames.get(currentTrack), Toast.LENGTH_LONG).show();
}
return null;
case 1:
try{
FileInputStream fis = new FileInputStream(new File(path, trackNames.get(currentTrack)));
FileDescriptor fileDescriptor = fis.getFD();
return new Music(fileDescriptor);
} catch(IOException e){
e.printStackTrace();
Toast.makeText(getBaseContext(), "Error Loading " + trackNames.get(currentTrack), Toast.LENGTH_LONG).show();
}
return null;
default:
return null;
}
}
//Sets the background image to match the track currently playing or a default image
private void setImage(String name) {
if(type == 0){
int imageResource = getResources().getIdentifier(name, null, getPackageName());
if(imageResource != 0){
Drawable image = getResources().getDrawable(imageResource);
bg.setImageDrawable(image);
} else{
int defaultImageResource = getResources().getIdentifier("drawable/defaultbg", null, getPackageName());
if(defaultImageResource != 0){
Drawable image = getResources().getDrawable(defaultImageResource);
bg.setImageDrawable(image);
}
}
} else if(type == 1){
if(new File(path2.getAbsolutePath(), trackArtworks.get(currentTrack) + ".jpg").exists()){
bg.setImageDrawable(Drawable.createFromPath(path2.getAbsolutePath() + "/" + trackArtworks.get(currentTrack) + ".jpg"));
} else{
int defaultImageResource = getResources().getIdentifier("drawable/defaultbg", null, getPackageName());
if(defaultImageResource != 0){
Drawable image = getResources().getDrawable(defaultImageResource);
bg.setImageDrawable(image);
}
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu){
super.onCreateOptionsMenu(menu);
createMenu(menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item){
switch(item.getItemId()){
case 0:
//Set Looping
synchronized(this){
if(track.isLooping()){
track.setLooping(false);
Toast.makeText(getBaseContext(), "Playing Tracks Sequentially", Toast.LENGTH_SHORT).show();
} else{
track.setLooping(true);
Toast.makeText(getBaseContext(), "Looping " + trackNames.get(currentTrack), Toast.LENGTH_SHORT).show();
}
}
return true;
case 1:
//Set Shuffle
synchronized(this){
if(shuffle){
setShuffle(false);
} else{
setShuffle(true);
}
}
return true;
case 2:
//Stop Music
synchronized(this){
track.switchTracks();
btnPlay.setBackgroundResource(R.drawable.play);
}
return true;
case 3:
//Change Source from Assets to SD Card and vice versa
synchronized(this){
type++;
if(type > 1){
type = 0;
}
}
if(type == 0){
Toast.makeText(getBaseContext(), "Loading Tracks from Assets ", Toast.LENGTH_SHORT).show();
} else if(type == 1){
Toast.makeText(getBaseContext(), "Loading Tracks from SD Card", Toast.LENGTH_SHORT).show();
}
initialize(type);
return true;
default:
return false;
}
}
private void createMenu(Menu menu){
MenuItem miLooping = menu.add(0, 0, 0, "Looping");{
miLooping.setIcon(R.drawable.looping);
}
MenuItem miShuffle = menu.add(0, 1, 1, "Shuffle");{
miShuffle.setIcon(R.drawable.shuffle);
}
MenuItem miStop = menu.add(0, 2, 2, "Stop");{
miStop.setIcon(R.drawable.stop);
}
MenuItem miSource = menu.add(0, 3, 3, "Source");{
miSource.setIcon(R.drawable.source);
}
}
public void click(View view){
int id = view.getId();
switch(id){
case R.id.btnPlay:
synchronized(this){
if(isTuning){
isTuning = false;
btnPlay.setBackgroundResource(R.drawable.play);
track.pause();
} else{
isTuning = true;
btnPlay.setBackgroundResource(R.drawable.pause);
playTrack();
}
}
return;
case R.id.btnPrevious:
setTrack(0);
loadTrack();
playTrack();
return;
case R.id.btnNext:
setTrack(1);
loadTrack();
playTrack();
return;
default:
return;
}
}
private void setTrack(int direction){
if(direction == 0){
currentTrack--;
if(currentTrack < 0){
currentTrack = trackNames.size()-1;
}
} else if(direction == 1){
currentTrack++;
if(currentTrack > trackNames.size()-1){
currentTrack = 0;
}
}
if(shuffle){
int temp = random.nextInt(trackNames.size());
while(true){
if(temp != currentTrack){
currentTrack = temp;
break;
}
temp++;
if(temp > trackNames.size()-1){
temp = 0;
}
}
}
}
//Plays the Track
private void playTrack(){
if(isTuning && track != null){
track.play();
Toast.makeText(getBaseContext(), "Playing " + trackNames.get(currentTrack).substring(0, trackNames.get(currentTrack).length()-4), Toast.LENGTH_SHORT).show();
}
}
//Simply sets shuffle to isShuffle and then displays a message for confirmation
private void setShuffle(boolean isShuffle) {
shuffle = isShuffle;
if(shuffle){
Toast.makeText(getBaseContext(), "Shuffle On", Toast.LENGTH_SHORT).show();
} else{
Toast.makeText(getBaseContext(), "Shuffle Off", Toast.LENGTH_SHORT).show();
}
}
}
有你'main.xml'文件有問題解決它，你應該罰款 – tyczj
我剛剛導入的項目，在這裏沒有任何問題...... – Melquiades