我创建了一个带有歌曲列表视图的音频播放器，当用户点击音乐播放器启动的列表视图中的项目时，以及一个暂停它的按钮，这一切都运行良好！
我的下一站我实现了一个搜索栏来更新歌曲的进度和两个文本视图，一个用于当前歌曲的持续时间，另一个用于歌曲的总持续时间。我已经写了代码，一切似乎都很好，但每次我运行它都会强行关闭
请帮忙！
.Java类
public class Nasheeds extends ListActivity implements OnCompletionListener, SeekBar.OnSeekBarChangeListener {
//ArrayList holds the data (as HashMaps) to load into the ListView
ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
//SimpleAdapter does the work to load the data in to the ListView
private SimpleAdapter sa;
private MediaPlayer mp;
public boolean istrue = true;
private ImageButton btnPrevious;
private ImageButton btnNext;
private SeekBar songProgressBar;
private TextView songCurrentDurationLabel;
private TextView songTotalDurationLabel;
//Handler to update UI timer, progress bar
private Handler mHandler = new Handler();;
private Utilities utils;
private int seekForwardTime = 5000; //500 milliseconds
private int seekBackwardTime = 5000;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.nasheeds2);
//HashMap links each line of data to the correct TextView
HashMap<String,String> item;
for(int i=0;i<Nasheed.length;i++){
item = new HashMap<String,String>();
item.put( "line1", Nasheed[i][0]);
item.put( "line2", Nasheed[i][1]);
list.add( item );
}
sa = new SimpleAdapter(this, list,
R.layout.nasheeds1,
new String[] { "line1","line2" },
new int[] {R.id.displayname, R.id.title});
setListAdapter(sa);
btnPrevious = (ImageButton) findViewById(R.id.prev);
btnNext = (ImageButton)findViewById(R.id.next);
songProgressBar = (SeekBar)findViewById(R.id.seekbar);
songCurrentDurationLabel = (TextView)findViewById(R.id.songCurrentDurationLabel);
songTotalDurationLabel = (TextView)findViewById(R.id.songTotalDurationLabel);
utils = new Utilities();
songProgressBar.setOnSeekBarChangeListener(this);
mp.setOnCompletionListener(this);
getListView().setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
switch (arg2)
{
case 0:
System.out.println("User selected option 1");
// mp.stop();
if (mp != null && mp.isPlaying()) {
mp.stop();
}else
mp = MediaPlayer.create(Nasheeds.this, R.raw.mok);
mp.start();
// MediaPlayer mp = MediaPlayer.create(Nasheeds.this, R.raw.mok);
// mp.start();
TextView tv=(TextView) findViewById(R.id.selectedfile);
tv.setText("Playing "+ "Mountains of Mekkah, Zain Bikha");
//set progress bar values
songProgressBar.setProgress(0);
songProgressBar.setMax(100);
//updating progress bar
updateProgressBar();
/* catch (IllegalArgumentException e){
e.printStackTrace();
} catch (IllegalStateException e){
e.printStackTrace();
} catch (IO Exception e){
e.printStackTrace();
}*/
break;
case 1:
System.out.println("User selected option 2");
if (mp != null && mp.isPlaying()) {
mp.stop();
}else
mp = MediaPlayer.create(Nasheeds.this, R.raw.hnim);
mp.start();
case 2:
break;
}
}
});
View playbtn = findViewById(R.id.play);
playbtn.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
if (istrue) {
mp.pause();
istrue = false;
} else {
mp.start();
istrue = true;
}
}
});
btnPrevious.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
/* if(currentSongIndex > 0){
playSong(currentSongIndex - 1);
currentSongIndex = currentSongIndex - 1;
}else{
// play last song
playSong(list.size() - 1);
currentSongIndex = list.size() - 1;
}*/
System.out.println("Click Works");
}
});
btnNext.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
System.out.println("Click Works");
}
});
}
public void updateProgressBar(){
mHandler.postDelayed(mUpdateTimeTask, 100);
}
private Runnable mUpdateTimeTask = new Runnable(){
public void run(){
long totalDuration = mp.getDuration();
long currentDuration = mp.getCurrentPosition();
//displaying total duration time
songTotalDurationLabel.setText(""+utils.milliSecondsToTimer(totalDuration));
//displaying time completed playing
songCurrentDurationLabel.setText(""+utils.milliSecondsToTimer(currentDuration));
//updating progress bar
int progress = (int)(utils.getProgressPercentage(currentDuration, totalDuration));
songProgressBar.setProgress(progress);
//running this thread after 100 milliseconds
mHandler.postDelayed(this, 100);
}
};
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
}
public void onStartTrackingTouch(SeekBar seekBar) {
mHandler.removeCallbacks(mUpdateTimeTask);
}
public void onStopTrackingTouch(SeekBar seekBar) {
mHandler.removeCallbacks(mUpdateTimeTask);
int totalDuration = mp.getDuration();
int currentPosition = utils.progressToTimer(seekBar.getProgress(), totalDuration);
mp.seekTo(currentPosition);
updateProgressBar();
}
private String[][] Nasheed =
{{"Mountains of Mekkah","Zain Bikha"},
{"His name is Mohammed","Kamal Uddin"},
{"Hadith 3",".....add hadith"},};
public void onCompletion(MediaPlayer mp) {
}
}
实用工具类
package com.example.fuelfinder;
public class Utilities {
/**
* Function to convert milliseconds time to
* Timer Format
* Hours:Minutes:Seconds
* */
public String milliSecondsToTimer(long milliseconds){
String finalTimerString = "";
String secondsString = "";
// Convert total duration into time
int hours = (int)( milliseconds / (1000*60*60));
int minutes = (int)(milliseconds % (1000*60*60)) / (1000*60);
int seconds = (int) ((milliseconds % (1000*60*60)) % (1000*60) / 1000);
// Add hours if there
if(hours > 0){
finalTimerString = hours + ":";
}
// Prepending 0 to seconds if it is one digit
if(seconds < 10){
secondsString = "0" + seconds;
}else{
secondsString = "" + seconds;}
finalTimerString = finalTimerString + minutes + ":" + secondsString;
// return timer string
return finalTimerString;
}
/**
* Function to get Progress percentage
* @param currentDuration
* @param totalDuration
* */
public int getProgressPercentage(long currentDuration, long totalDuration){
Double percentage = (double) 0;
long currentSeconds = (int) (currentDuration / 1000);
long totalSeconds = (int) (totalDuration / 1000);
// calculating percentage
percentage =(((double)currentSeconds)/totalSeconds)*100;
// return percentage
return percentage.intValue();
}
/**
* Function to change progress to timer
* @param progress -
* @param totalDuration
* returns current duration in milliseconds
* */
public int progressToTimer(int progress, int totalDuration) {
int currentDuration = 0;
totalDuration = (int) (totalDuration / 1000);
currentDuration = (int) ((((double)progress) / 100) * totalDuration);
// return current duration in milliseconds
return currentDuration * 1000;
}
}
xml文件1
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/displayname"
android:textSize="18dip"
android:textStyle="bold"
android:singleLine="true"
android:ellipsize="end"/>
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/title"
android:textSize="15dip"
android:singleLine="true"
android:ellipsize="end"
android:layout_weight="1.0"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/duration"
android:gravity="right"
android:textSize="15dip"
android:singleLine="true"
android:ellipsize="end"/>
</LinearLayout>
</LinearLayout>
第二个xml文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ListView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@android:id/list"
android:layout_weight="1.0"
/>
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@android:drawable/screen_background_light"
android:padding="10dip">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/selectedfile"
android:text="Not file selected"
android:textColor="@android:color/black"
android:gravity="center_horizontal"
android:singleLine="true"
android:ellipsize="middle"/>
<SeekBar
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/seekbar"
android:max="100"
android:paddingBottom="10dip"/>
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:background="@android:drawable/screen_background_light">
<TextView
android:id="@+id/songCurrentDurationLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/prev"
android:src="@android:drawable/ic_media_previous"
android:onClick="doClick"/>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/play"
android:src="@android:drawable/ic_media_play"
android:onClick="onClick"/>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/next"
android:src="@android:drawable/ic_media_next"
android:onClick="doClick"/>
<TextView
android:id="@+id/songTotalDurationLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</LinearLayout>
</LinearLayout>
LogCat：
12-07 14:43:02.262: E/AndroidRuntime(1009): FATAL EXCEPTION: main
12-07 14:43:02.262: E/AndroidRuntime(1009): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fuelfinder/com.example.fuelfinder.Nasheeds}: java.lang.NullPointerException
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.ActivityThread.access$600(ActivityThread.java:130)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.os.Handler.dispatchMessage(Handler.java:99)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.os.Looper.loop(Looper.java:137)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.ActivityThread.main(ActivityThread.java:4745)
12-07 14:43:02.262: E/AndroidRuntime(1009): at java.lang.reflect.Method.invokeNative(Native Method)
12-07 14:43:02.262: E/AndroidRuntime(1009): at java.lang.reflect.Method.invoke(Method.java:511)
12-07 14:43:02.262: E/AndroidRuntime(1009): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-07 14:43:02.262: E/AndroidRuntime(1009): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-07 14:43:02.262: E/AndroidRuntime(1009): at dalvik.system.NativeStart.main(Native Method)
12-07 14:43:02.262: E/AndroidRuntime(1009): Caused by: java.lang.NullPointerException
12-07 14:43:02.262: E/AndroidRuntime(1009): at com.example.fuelfinder.Nasheeds.onCreate(Nasheeds.java:79)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.Activity.performCreate(Activity.java:5008)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
12-07 14:43:02.262: E/AndroidRuntime(1009): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
12-07 14:43:02.262: E/AndroidRuntime(1009): ... 11 more
答案 0 :(得分：0)
由于StackOverflow没有行号，因此很难具体说明发生了什么，但异常中的违规行很明显：
12-07 14：43：02.262：E / AndroidRuntime（1009）：引起：java.lang.NullPointerException 12-07 14：43：02.262：E / AndroidRuntime（1009）：at com.example.fuelfinder.Nasheeds.onCreate（Nasheeds.java:79）
我有一种感觉，如果你在那里设置断点，你将能够很快找到问题。