java Android Studio在警报准备就绪时启动Mediaplayer
你好，我有2个活动，2个应用程序，每个都有它们的类（总共大约10个类），我想把它们结合起来。我有一个功能性闹钟和一个功能性媒体播放器。我想在闹钟响的时候启动mediaplayer。问题是我的应用程序在响的时候崩溃了。 媒体播放器类：
package com.never.mediaalarmplayer;
import 安卓.content.ComponentName;
import 安卓.content.ContentResolver;
import 安卓.content.Context;
import 安卓.content.Intent;
import 安卓.content.ServiceConnection;
import 安卓.database.Cursor;
import 安卓.net.Uri;
import 安卓.os.Bundle;
import 安卓.os.IBinder;
import 安卓.support.v7.app.AppCompatActivity;
import 安卓.view.MenuItem;
import 安卓.view.View;
import 安卓.widget.Button;
import 安卓.widget.ListView;
import 安卓.widget.MediaController;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
/**
* Created by Never on 5/14/2017.
*/
public class MediaPlayer extends AppCompatActivity implements MediaController.MediaPlayerControl {
private ArrayList<Song> songList;
private ListView songView;
private MusicService musicSrv;
private Intent playIntent;
private boolean musicBound=false;
private MusicController controller;
private boolean paused=false, playbackPaused=false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mediaplayer);
songView = (ListView)findViewById(R.id.song_list);
songList = new ArrayList<>();
getSongList();
Collections.sort(songList, new Comparator<Song>(){
public int compare(Song a, Song b){
return a.getTitle().compareTo(b.getTitle());
}
});
SongAdapter songAdt = new SongAdapter(this, songList);
songView.setAdapter(songAdt);
setController();
Button btn = (Button)findViewById(R.id.open_alarm);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(MediaPlayer.this, Alarm.class));
}
});
}
//connect to the service
private ServiceConnection musicConnection = new ServiceConnection(){
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
MusicService.MusicBinder binder = (MusicService.MusicBinder)service;
//get service
musicSrv = binder.getService();
//pass list
musicSrv.setList(songList);
musicBound = true;
}
@Override
public void onServiceDisconnected(ComponentName name) {
musicBound = false;
}
};
@Override
protected void onStart() {
super.onStart();
if(playIntent==null){
playIntent = new Intent(this, MusicService.class);
bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
startService(playIntent);
}
}
@Override
protected void onPause(){
super.onPause();
paused=true;
}
@Override
protected void onResume(){
super.onResume();
if(paused){
setController();
paused=false;
}
}
@Override
protected void onStop(){
controller.hide();
super.onStop();
}
public void songPicked(View view){
musicSrv.setSong(Integer.parseInt(view.getTag().toString()));
musicSrv.playSong();
if(playbackPaused){
setController();
playbackPaused=false;
}
controller.show(0);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
//menu item selected
switch (item.getItemId()) {
case R.id.action_shuffle:
//shuffle
musicSrv.setShuffle();
break;
case R.id.action_end:
stopService(playIntent);
musicSrv=null;
System.exit(0);
break;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onDestroy() {
stopService(playIntent);
musicSrv=null;
super.onDestroy();
}
public void getSongList() {
//retrieve song info
ContentResolver musicResolver = getContentResolver();
Uri musicUri = 安卓.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
if(musicCursor!=null && musicCursor.moveToFirst()){
//get columns
int titleColumn = musicCursor.getColumnIndex
(安卓.provider.MediaStore.Audio.Media.TITLE);
int idColumn = musicCursor.getColumnIndex
(安卓.provider.MediaStore.Audio.Media._ID);
int artistColumn = musicCursor.getColumnIndex
(安卓.provider.MediaStore.Audio.Media.ARTIST);
//add songs to list
do {
long thisId = musicCursor.getLong(idColumn);
String thisTitle = musicCursor.getString(titleColumn);
String thisArtist = musicCursor.getString(artistColumn);
songList.add(new Song(thisId, thisTitle, thisArtist));
}
while (musicCursor.moveToNext());
}
}
private void setController(){
//set the controller up
controller = new MusicController(this);
controller.setPrevNextListeners(new View.OnClickListener() {
@Override
public void onClick(View v) {
playNext();
}
}, new View.OnClickListener(){
@Override
public void onClick(View v){
playPrev();
}
});
controller.setMediaPlayer(this);
controller.setAnchorView(findViewById(R.id.song_list));
controller.setEnabled(true);
}
//play next
private void playNext(){
musicSrv.playNext();
if(playbackPaused){
setController();
playbackPaused=false;
}
controller.show(0);
}
//play prev
private void playPrev(){
musicSrv.playPrev();
if(playbackPaused) {
setController();
playbackPaused = false;
}
controller.show(0);
}
@Override
public void start() {
musicSrv.go();
}
@Override
public void pause() {
playbackPaused=true;
musicSrv.pausePlayer();;
}
@Override
public int getDuration() {
if(musicSrv!=null &&musicBound&&musicSrv.isPng())
return musicSrv.getDur();
else
return 0;
}
@Override
public int getCurrentPosition() {
if(musicSrv!=null&&musicBound&&musicSrv.isPng())
return musicSrv.getPosn();
else
return 0;
}
@Override
public void seekTo(int pos) {
musicSrv.seek(pos);
}
@Override
public boolean isPlaying() {
if(musicSrv!=null&&musicBound)
return musicSrv.isPng();
else
return false;
}
@Override
public int getBufferPercentage() {
return 0;
}
@Override
public boolean canPause() {
return true;
}
@Override
public boolean canSeekBackward() {
return true;
}
@Override
public boolean canSeekForward() {
return true;
}
@Override
public int getAudioSessionId() {
return 0;
}
}
报警接收器等级：
package com.never.mediaalarmplayer;
import 安卓.content.Context;
import 安卓.content.Intent;
import 安卓.media.Ringtone;
import 安卓.media.RingtoneManager;
import 安卓.net.Uri;
import 安卓.support.v4.content.WakefulBroadcastReceiver;
/**
* Created by Never on 4/29/2017.
*/
public class AlarmReceiver extends WakefulBroadcastReceiver{
private static Ringtone ringtone = null;
@Override
public void onReceive(Context context, Intent intent) {
Alarm.getTextView2().setText("It's time to wake up!");
Uri uri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
ringtone = RingtoneManager.getRingtone(context, uri);
// ringtone.play();
MediaPlayer ms = new MediaPlayer();
ms.onStart();
}
public static void stopRingtone() {
ringtone.stop();
}
}
和报警等级：
package com.never.mediaalarmplayer;
import 安卓.annotation.TargetApi;
import 安卓.app.AlarmManager;
import 安卓.app.PendingIntent;
import 安卓.content.Intent;
import 安卓.os.Build;
import 安卓.os.Message;
import 安卓.support.v4.app.FragmentManager;
import 安卓.support.v4.app.FragmentTransaction;
import 安卓.support.v7.app.AppCompatActivity;
import 安卓.os.Bundle;
import 安卓.os.Handler;
import 安卓.view.View;
import 安卓.widget.Button;
import 安卓.widget.TextView;
import 安卓.view.View.OnClickListener;
import java.util.Calendar;
public class Alarm extends AppCompatActivity {
private static int timeHour = Calendar.getInstance().get(Calendar.HOUR_OF_DAY);
private static int timeMinute = Calendar.getInstance().get(Calendar.MINUTE);
TextView textView1;
private static TextView textView2;
public static TextView getTextView2(){
return textView2;
}
AlarmManager alarmManager;
private PendingIntent pendingIntent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setam layoutul pe care ne uitam si pe care lucram
setContentView(R.layout.activity_alarm);
// spunem ca textView1 este textviewul cu id-ul msg1
textView1 = (TextView)findViewById(R.id.msg1);
// afisam ora curenta
if(timeHour>9&&timeMinute>9)
textView1.setText(timeHour + ":" + timeMinute);
else if(timeHour>9&&timeMinute<=9)
textView1.setText(timeHour + ":" + "0" + timeMinute);
else if(timeHour<=9&&timeMinute>9)
textView1.setText("0" + timeHour + ":" + timeMinute);
else if(timeHour<=9&&timeMinute<=9)
textView1.setText("0" + timeHour + ":" + "0" + timeMinute);
textView2 = (TextView) findViewById(R.id.msg2);
alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
Intent myIntent = new Intent (Alarm.this,AlarmReceiver.class);
pendingIntent = PendingIntent.getBroadcast(Alarm.this,0,myIntent,0);
OnClickListener listener1 = new OnClickListener(){
@Override
public void onClick(View v) {
textView2.setText("");
Bundle bundle = new Bundle();
bundle.putInt(MyConstants.HOUR, timeHour);
bundle.putInt(MyConstants.MINUTE, timeMinute);
MyDialogFragment fragment = new MyDialogFragment(new MyHandler());
fragment.setArguments(bundle);
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.add(fragment, MyConstants.TIME_PICKER);
transaction.commit();
}
};
Button btn1 = (Button)findViewById(R.id.button1);
btn1.setOnClickListener(listener1);
OnClickListener listener2 = new OnClickListener() {
@Override
public void onClick(View v) {
textView2.setText("");
cancelAlarm();
}
};
Button btn2 = (Button)findViewById(R.id.button2);
btn2.setOnClickListener(listener2);
Button btn = (Button)findViewById(R.id.open_mp);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(Alarm.this, MediaPlayer.class));
}
});
}
//A Handler allows you to send and process Message and Runnable objects associated with a thread's MessageQueue.
//There are two main uses for a Handler: (1) to schedule messages and runnables to be executed as some point in the future; and (2) to enqueue an action to be performed on a different thread than your own.
//Practic folosim un handler pentru a afisa ora la care am setat alarma dupa ce am setat-o
class MyHandler extends Handler
{
@Override
public void handleMessage (Message msg){
//A mapping from String keys to various Parcelable values.
//Bundle getBundle (String key)
//Returns the value associated with the given key, or null if no mapping of the desired type exists for the given key or a null value is explicitly associated with the key.
Bundle bundle = msg.getData();
//preluam ora si minutul la care am setat alarma
timeHour=bundle.getInt(MyConstants.HOUR);
timeMinute = bundle.getInt(MyConstants.MINUTE);
//afisam ora la care am setat alarma
if(timeHour>9&&timeMinute>9)
textView1.setText(timeHour + ":" + timeMinute);
else if(timeHour>9&&timeMinute<=9)
textView1.setText(timeHour + ":" + "0" + timeMinute);
else if(timeHour<=9&&timeMinute>9)
textView1.setText("0" + timeHour + ":" + timeMinute);
else if(timeHour<=9&&timeMinute<=9)
textView1.setText("0" + timeHour + ":" + "0" + timeMinute);
setAlarm();
}
}
@TargetApi(Build.VERSION_CODES.KITKAT)
private void setAlarm(){
// getInstance()
//Gets a calendar using the default time zone and locale.
Calendar calendar = Calendar.getInstance();
// set(int field, int value)
// Sets the given calendar field to the given value.
calendar.set(Calendar.HOUR_OF_DAY,timeHour);
calendar.set(Calendar.MINUTE,timeMinute);
// setExact(int type, long triggerAtMillis, PendingIntent operation)
// Schedules the alarm and if there is already an alarm by the intent then previous one will be canceled.
//RTC_WAKEUP
//It is used to fire pending intent at specified time forcing the phone to wake up.
//Practic prin linia asta de cod setam alarma si verificam daca ora curenta este egala cu ora programata pentru trezire si in caz afirmativ trimitem semnalul(pendingintent) ce este legat la intent astfel stim ca trebuie trimis catre AlarmRceiver, in acelasi timp ii spunem sa "trezeasca" telefonul
alarmManager.setExact(
//ii spunem sa "trezeasca telefonul" in cazul in care trebuie sa sune alarma
AlarmManager.RTC_WAKEUP,
// preluam ora la care setam alarma si retinem totul transformat in milisecunde
calendar.getTimeInMillis(),
//verificam daca este timpul sa sunam alarma
pendingIntent);
}
private void cancelAlarm(){
if(alarmManager!=null){
alarmManager.cancel(pendingIntent);
pendingIntent.cancel();
AlarmReceiver.stopRingtone();
}
}
}
例外情况：
07-11 10:43:43.392 1915-1915/com.never.mediaalarmplayer D/Ringtone: Successfully created local player
07-11 10:43:43.397 1915-1915/com.never.mediaalarmplayer D/AndroidRuntime: Shutting down VM
07-11 10:43:43.397 1915-1915/com.never.mediaalarmplayer E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.never.mediaalarmplayer, PID: 1915
java.lang.RuntimeException: Unable to start receiver com.never.mediaalarmplayer.AlarmReceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'void 安卓.app.Application.dispatchActivityStarted(安卓.app.Activity)' on a null object reference
at 安卓.app.ActivityThread.handleReceiver(ActivityThread.java:2732)
at 安卓.app.ActivityThread.-wrap14(ActivityThread.java)
at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
at 安卓.os.Handler.dispatchMessage(Handler.java:102)
at 安卓.os.Looper.loop(Looper.java:148)
at 安卓.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void 安卓.app.Application.dispatchActivityStarted(安卓.app.Activity)' on a null object reference
at 安卓.app.Activity.onStart(Activity.java:1146)
at 安卓.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:595)
at 安卓.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
at com.never.mediaalarmplayer.MediaPlayer.onStart(MediaPlayer.java:78)
at com.never.mediaalarmplayer.AlarmReceiver.onReceive(AlarmReceiver.java:23)
at 安卓.app.ActivityThread.handleReceiver(ActivityThread.java:2725)
at 安卓.app.ActivityThread.-wrap14(ActivityThread.java)
at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
at 安卓.os.Handler.dispatchMessage(Handler.java:102)
at 安卓.os.Looper.loop(Looper.java:148)
at 安卓.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:616)
这是我第一次发帖，所以如果有任何问题，我会编辑它，也非常感谢你
# 1 楼答案
活动不是像在AlarmReceiver类的
onReceive中那样启动的，即它们由
Context.startActivity (Intent)开始。android系统负责启动这些活动，因为它管理一堆活动，并为这些活动发布生命周期回调。因为您自己开始活动，所以您错过了最初的生命周期回调，例如onCreate