我尝试在Android studio 3.0中使用视频教程创建一个警报，我做了同样的事情，应用程序将运行，但是当我点击“警报”时它将被关闭。任何人都告诉我，在哪里问题是什么？ 我曾使用Emulator API 22和23进行过尝试。
我当然不是，但我认为，问题应该在RingtonePlayingservice和getString中，因为它给出了一个错误“方法调用getString可能会产生java.lang.nullpointer” 但我，我不确定，如果问题是，我该如何解决？
我的主动：
package com.example.standard.alarm;
public class MainActivity extends AppCompatActivity {
//to make our Alarmmanager;
AlarmManager alarm_manager;
DatePicker alarm_datepicker;
TimePicker alarm_timepicker;
TextView update_text;
Context context;
PendingIntent pending_intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.context = this;
//initialize our Alarmmanager
alarm_manager = (AlarmManager) getSystemService(ALARM_SERVICE);
//initialize our DatePicker
alarm_datepicker = findViewById(R.id.datePicker);
alarm_timepicker = findViewById(R.id.timePicker);
//initialize our textupdate
update_text = findViewById(R.id.update_text);
//Create an instance of c Calender
final Calendar calendar = Calendar.getInstance();
final Intent my_intent = new Intent(this.context , Alarm_Receiver.class);
Button alarm_on = findViewById(R.id.alarm_on);
alarm_on.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (VERSION.SDK_INT >= 23 ) {
calendar.set(Calendar.YEAR, alarm_datepicker.getYear());
calendar.set(Calendar.MONTH, alarm_datepicker.getMonth());
calendar.set(Calendar.DAY_OF_MONTH, alarm_datepicker.getDayOfMonth());
calendar.set(Calendar.HOUR_OF_DAY, alarm_timepicker.getHour());
calendar.set(Calendar.MINUTE, alarm_timepicker.getMinute());
int year = alarm_datepicker.getYear();
int month = alarm_datepicker.getMonth()+1;
int day = alarm_datepicker.getDayOfMonth();
int hour = alarm_timepicker.getHour();
int minute = alarm_timepicker.getMinute();
String yearst = String.valueOf(year);
String monthst = String.valueOf(month);
String dayst = String.valueOf(day);
String hourst = String.valueOf(hour);
String minutest = String.valueOf(minute);
set_alarm_text("Alarm set on"+yearst+"/"+monthst+"/"+dayst+" - "+hourst+":"+minutest);
}else{
calendar.set(Calendar.YEAR , alarm_datepicker.getYear());
calendar.set(Calendar.MONTH , alarm_datepicker.getMonth());
calendar.set(Calendar.DAY_OF_MONTH , alarm_datepicker.getDayOfMonth());
calendar.set(Calendar.HOUR_OF_DAY , alarm_timepicker.getCurrentHour());
calendar.set(Calendar.MINUTE , alarm_timepicker.getCurrentMinute());
int yearl = alarm_datepicker.getYear();
int monthl = alarm_datepicker.getMonth()+1;
int dayl = alarm_datepicker.getDayOfMonth();
int hourl = alarm_timepicker.getCurrentHour();
int minutel = alarm_timepicker.getCurrentMinute();
String yearlst = String.valueOf(yearl);
String monthlst = String.valueOf(monthl);
String daylst = String.valueOf(dayl);
String hourlst = String.valueOf(hourl);
String minutelst = String.valueOf(minutel);
set_alarm_text("Alarm set on"+yearlst+"/"+monthlst+"/"+daylst+" - "+hourlst+":"+minutelst);
}
my_intent.putExtra("extra","alarm on");
pending_intent = PendingIntent.getBroadcast(MainActivity.this , 0 ,
my_intent, PendingIntent.FLAG_UPDATE_CURRENT);
alarm_manager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
pending_intent);
}
});
Button alarm_off = findViewById(R.id.alarm_off);
alarm_off.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
set_alarm_text("Alarm Off");
alarm_manager.cancel(pending_intent);
my_intent.putExtra("extra","alarm off");
sendBroadcast(my_intent);
}
});
}
private void set_alarm_text(String output) {
update_text.setText(output);
}
}
我的服务类是：
public class RingtonePlayingService extends Service {
MediaPlayer media_song;
int startId;
Boolean isRunning;
@Nullable
@Override
public IBinder onBind(Intent intent){return null;}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i("LocalService", "Received start id " + startId + ": " + intent);
//fetch the extra string values
String state = intent.getExtras().getString("extra");
Log.e("Ringtone extra is",state);
assert state != null;
switch (state) {
case "alarm on":
startId = 1;
break;
case "alarm off":
startId = 0;
break;
default:
startId = 0;
break;
}
if (!this.isRunning && startId == 1){
media_song = MediaPlayer.create(this, R.raw.penii);
media_song.start();
this.isRunning = true;
this.startId = 0;
}else if (this.isRunning && startId == 0){
media_song.stop();
media_song.reset();
this.isRunning = false;
this.startId = 0;
}else if (!this.isRunning && startId == 0){
this.isRunning = false;
this.startId = 0;
}else if (this.isRunning && startId == 1){
this.isRunning = true;
this.startId = 1;
}else {
}
return START_NOT_STICKY;
}
@Override
public void onDestroy() {
super.onDestroy();
this.isRunning = false;
}
}
我的接收者是：
package com.example.standard.alarm;
public class Alarm_Receiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Log.e("Hi we are in receiver","Yay correct");
String get_your_String = intent.getExtras().getString("extra");
Log.e("what is the keay", get_your_String);
Intent service_intent = new Intent(context, RingtonePlayingService.class);
service_intent.putExtra("extra", get_your_String);
context.startService(service_intent);
}
}
和我的清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.standard.alarm">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver android:name=".Alarm_Receiver" />
<service android:name=".RingtonePlayingService"
android:enabled="true">
</service>
</application>
</manifest>
我的MainActivity XML是：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.standard.alarm.MainActivity">
<DatePicker
android:id="@+id/datePicker"
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/alarm_on"
android:clickable="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:text="alarm on"
android:textAppearance="@style/TextAppearance.AppCompat.Large"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/datePicker"
android:layout_marginLeft="8dp" />
<Button
android:id="@+id/alarm_off"
android:clickable="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:text="alarm off"
android:textAppearance="@style/TextAppearance.AppCompat.Large"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toBottomOf="@+id/datePicker"
android:layout_marginRight="8dp" />
<TextView
android:id="@+id/update_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="@style/TextAppearance.AppCompat.Large"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="45dp"
android:text="@string/did_you_set_the_alarm"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/datePicker" />
<TimePicker
android:id="@+id/timePicker"
android:layout_width="match_parent"
android:layout_height="310dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toBottomOf="@+id/update_text" />
</android.support.constraint.ConstraintLayout>
和Logcats中的错误：
FATAL EXCEPTION: main
Process: com.example.standard.alarm, PID: 4001
java.lang.RuntimeException: Unable to start service com.example.standard.alarm.RingtonePlayingService@e431d8d with Intent { cmp=com.example.standard.alarm/.RingtonePlayingService (has extras) }: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3027)
at android.app.ActivityThread.-wrap17(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1442)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
at com.example.standard.alarm.RingtonePlayingService.onStartCommand(RingtonePlayingService.java:49)
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3010)
at android.app.ActivityThread.-wrap17(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1442)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
答案 0 :(得分：0)
您还将MainActivity代码放在服务代码的位置...... 除了你似乎想要在null对象上调用booleanValue（）函数。在你的RingtonePlayingService的第49行