我是android studio的新手，因为这行代码
，我的应用程序崩溃了 songProgressBar.setOnSeekBarChangeListener(this);
在这里发布一个问题让我意识到这是一个在我的布局中带有id的拼写错误。好吧，这是我的布局代码，其中songProgressBar为id。
<SeekBar
android:id="@+id/songProgressBar"
android:layout_width="fill_parent"
android:layout_height="25dp"
android:layout_marginRight="15dp"
android:layout_marginLeft="15dp"
android:layout_above="@id/player_footer_bg"
android:thumb="@drawable/seek_handler"
android:progressDrawable="@drawable/seekbar_progress_blue"
android:paddingLeft="6dp"
android:paddingRight="6dp"/>
现在，我不知道拼写错误是什么，我也不知道我应该做什么。告诉我这是一个拼写错误的人说我应该检查活动运行时组件是否存在于布局中。我不知道我现在要做什么。
这是我的MainAcivity。
public class MainActivity extends AppCompatActivity implements MediaPlayer.OnCompletionListener, SeekBar.OnSeekBarChangeListener {
private ImageButton btnPlay;
private ImageButton btnForward;
private ImageButton btnBackward;
private ImageButton btnNext;
private ImageButton btnPrevious;
private ImageButton btnPlaylist;
private ImageButton btnRepeat;
private ImageButton btnShuffle;
private SeekBar songProgressBar;
private TextView songTitleLabel;
private TextView songCurrentDurationLabel;
private TextView songTotalDurationLabel;
private MediaPlayer mp;
private Handler mHandler = new Handler();
private SongsManager songManager;
private Utilities utils;
private int seekForwardTime = 5000;
private int seekBackwardTime = 5000;
private int currentSongIndex = 0;
private boolean isShuffle = false;
private boolean isRepeat = false;
private ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
btnPlay = (ImageButton) findViewById(R.id.btnPlay);
btnForward = (ImageButton) findViewById(R.id.btnForward);
btnBackward = (ImageButton) findViewById(R.id.btnBackward);
btnNext = (ImageButton) findViewById(R.id.btnNext);
btnPrevious = (ImageButton) findViewById(R.id.btnPrevious);
btnPlaylist = (ImageButton) findViewById(R.id.btnPlaylist);
btnRepeat = (ImageButton) findViewById(R.id.btnRepeat);
btnShuffle = (ImageButton) findViewById(R.id.btnShuffle);
songProgressBar = (SeekBar) findViewById(R.id.songProgressBar);
songTitleLabel = (TextView) findViewById(R.id.songTitle);
songCurrentDurationLabel = (TextView) findViewById(R.id.songCurrentDurationLabel);
songTotalDurationLabel = (TextView) findViewById(R.id.songTotalDurationLabel);
mp = new MediaPlayer();
songManager = new SongsManager();
utils = new Utilities();
songProgressBar.setOnSeekBarChangeListener(this);
mp.setOnCompletionListener(this);
songsList = songManager.getPlayList();
playSong(0);
btnPlay.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
if(mp.isPlaying()){
if(mp!=null){
mp.pause();
btnPlay.setImageResource(R.drawable.btn_play);
}
}else{
if(mp!=null){
mp.start();
btnPlay.setImageResource(R.drawable.btn_pause);
}
}
}
});
btnForward.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
int currentPosition = mp.getCurrentPosition();
if(currentPosition + seekForwardTime <= mp.getDuration()){
mp.seekTo(currentPosition + seekForwardTime);
}else{
mp.seekTo(mp.getDuration());
}
}
});
btnBackward.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
int currentPosition = mp.getCurrentPosition();
if(currentPosition - seekBackwardTime >= 0){
mp.seekTo(currentPosition - seekBackwardTime);
}else{
mp.seekTo(0);
}
}
});
btnNext.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
if(currentSongIndex < (songsList.size() - 1)){
playSong(currentSongIndex + 1);
currentSongIndex = currentSongIndex + 1;
}else{
playSong(0);
currentSongIndex = 0;
}
}
});
btnPrevious.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
if(currentSongIndex > 0){
playSong(currentSongIndex - 1);
currentSongIndex = currentSongIndex - 1;
}else{
playSong(songsList.size() - 1);
currentSongIndex = songsList.size() - 1;
}
}
});
btnRepeat.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
if(isRepeat){
isRepeat = false;
Toast.makeText(getApplicationContext(), "Repeat is OFF", Toast.LENGTH_SHORT).show();
btnRepeat.setImageResource(R.drawable.btn_repeat);
}else{
isRepeat = true;
Toast.makeText(getApplicationContext(), "Repeat is ON", Toast.LENGTH_SHORT).show();
isShuffle = false;
btnRepeat.setImageResource(R.drawable.btn_repeat_focused);
btnShuffle.setImageResource(R.drawable.btn_shuffle);
}
}
});
btnShuffle.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
if(isShuffle){
isShuffle = false;
Toast.makeText(getApplicationContext(), "Shuffle is OFF", Toast.LENGTH_SHORT).show();
btnShuffle.setImageResource(R.drawable.btn_shuffle);
}else{
isShuffle= true;
Toast.makeText(getApplicationContext(), "Shuffle is ON", Toast.LENGTH_SHORT).show();
isRepeat = false;
btnShuffle.setImageResource(R.drawable.btn_shuffle_focused);
btnRepeat.setImageResource(R.drawable.btn_repeat);
}
}
});
btnPlaylist.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent i = new Intent(getApplicationContext(), PlayListActivity.class);
startActivityForResult(i, 100);
}
});
}
@Override
protected void onActivityResult(int requestCode,
int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(resultCode == 100){
currentSongIndex = data.getExtras().getInt("songIndex");
playSong(currentSongIndex);
}
}
public void playSong(int songIndex){
try {
mp.reset();
mp.setDataSource(songsList.get(songIndex).get("songPath"));
mp.prepare();
mp.start();
String songTitle = songsList.get(songIndex).get("songTitle");
songTitleLabel.setText(songTitle);
btnPlay.setImageResource(R.drawable.btn_pause);
songProgressBar.setProgress(0);
songProgressBar.setMax(100);
updateProgressBar();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void updateProgressBar() {
mHandler.postDelayed(mUpdateTimeTask, 100);
}
private Runnable mUpdateTimeTask = new Runnable() {
public void run() {
long totalDuration = mp.getDuration();
long currentDuration = mp.getCurrentPosition();
songTotalDurationLabel.setText(""+utils.milliSecondsToTimer(totalDuration));
songCurrentDurationLabel.setText(""+utils.milliSecondsToTimer(currentDuration));
int progress = (int)(utils.getProgressPercentage(currentDuration, totalDuration));
songProgressBar.setProgress(progress);
mHandler.postDelayed(this, 100);
}
};
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromTouch) {
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
mHandler.removeCallbacks(mUpdateTimeTask);
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
mHandler.removeCallbacks(mUpdateTimeTask);
int totalDuration = mp.getDuration();
int currentPosition = utils.progressToTimer(seekBar.getProgress(), totalDuration);
mp.seekTo(currentPosition);
updateProgressBar();
}
@Override
public void onCompletion(MediaPlayer arg0) {
if(isRepeat){
playSong(currentSongIndex);
} else if(isShuffle){
Random rand = new Random();
currentSongIndex = rand.nextInt((songsList.size() - 1) - 0 + 1) + 0;
playSong(currentSongIndex);
} else{
if(currentSongIndex < (songsList.size() - 1)){
playSong(currentSongIndex + 1);
currentSongIndex = currentSongIndex + 1;
}else{
playSong(0);
currentSongIndex = 0;
}
}
}
答案 0 :(得分：0)
我认为this是您之前提出的NullPointerException问题。将来，当您询问有关异常的问题时，您需要显示堆栈跟踪。
确保onCreate()调用sectContentView()的布局包含SeekBar，并使用findViewById为{ID调用SeekBar 1}}。像这个骨架的东西：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // This must be the layout that contains the SeekBar.
SeekBar songProgressBar = findViewById(R.id.songProgressBar);
songProgressBar.setOnSeekBarChangeListener(this);
}