铃声模式更改应用程序无法按预期工作

Question

我制作了一个小型应用程序，它以TimePicker的形式接收用户的输入，并将其存储在变量中，这些变量稍后用于触发警报，该警报将使振铃器保持在所需模式，直到需要为止。

但每当我尝试在AVD上运行它时，每当我按下任何按钮时，它都会不断崩溃，无论是静音还是振动。

MainActivity.java文件：

package com.example.android.implementingringermechanism;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.media.AudioManager;    
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TimePicker;
import android.widget.Toast;
import java.util.Calendar;
public class MainActivity extends AppCompatActivity {
//TimePicker to take time input from user when dialog activity pops
TimePicker picker;
//Buttons to change mode to silent or vibrate
Button silentButton, vibrateButton;
//Variables to store hours and minutes chosen by user
private int hour, minute;
//AudioManager instance used to change ringer mode
private AudioManager mAudioManager;
//AlarmManager instance used to set alarm to background task
AlarmManager mgr;
//Calendar instance to manipulate time for alarm with user input
Calendar time;
//PendingIntent to start when alarm is finished
private PendingIntent pendingIntent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
picker = (TimePicker) findViewById(R.id.timePicker);
//TimePicker will show time in 24 hour mode
picker.setIs24HourView(true);
silentButton = (Button) findViewById(R.id.silentButton);
vibrateButton = (Button) findViewById(R.id.vibrateButton);
//AlarmManager instance created to set an alarm for changing ringer mode back to normal
mgr = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(this, MyAlarmReceiver.class);
pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0);
time = Calendar.getInstance();
time.setTimeInMillis(System.currentTimeMillis());
}
public void silent(View view){
if(Build.VERSION.SDK_INT >= 23){
hour = picker.getHour();
minute = picker.getMinute();
}
else {
hour = picker.getCurrentHour();
minute = picker.getCurrentMinute();
}
mAudioManager.setRingerMode(AudioManager.RINGER_MODE_SILENT);
Toast.makeText(this, "Silent mode till " + hour + ":" + minute, Toast.LENGTH_LONG).show();
time.add(Calendar.HOUR, hour);
time.add(Calendar.MINUTE, minute);
mgr.set(AlarmManager.RTC_WAKEUP, time.getTimeInMillis(), pendingIntent);
}
public void vibrate(View view) {
if(Build.VERSION.SDK_INT >= 23){
hour = picker.getHour();
minute = picker.getMinute();
}
else {
hour = picker.getCurrentHour();
minute = picker.getCurrentMinute();
}
mAudioManager.setRingerMode(AudioManager.RINGER_MODE_VIBRATE);
Toast.makeText(this, "Vibrate mode till " + hour + ":" + minute, Toast.LENGTH_LONG).show();
time.add(Calendar.HOUR, hour);
time.add(Calendar.MINUTE, minute);
mgr.set(AlarmManager.RTC_WAKEUP, time.getTimeInMillis(), pendingIntent);
}
}

activity_main.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="wrap_content"
tools:context=".MainActivity"
android:layout_gravity="center"
android:orientation="vertical"
>
<TimePicker
android:id="@+id/timePicker"
android:layout_width="273dp"
android:layout_height="368dp"
android:layout_marginLeft="40dp" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/silentButton"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:layout_marginLeft="40dp"
android:text="@string/silentText"
android:textStyle="bold"
android:onClick="silent"/>
<Button
android:id="@+id/vibrateButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="100dp"
android:text="@string/vibrateText"
android:textStyle="bold"
android:onClick="vibrate"
/>

</LinearLayout>
</LinearLayout>

AndroidManifest.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.implementingringermechanism">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/setTime"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.AppCompat.Dialog">
<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=".MyAlarmReceiver" />
</application>
<uses-permission android:name="android.permission.ACCESS_NOTIFICATION_POLICY" />
</manifest>

MyAlarmReceiver.java文件：

package com.example.android.implementingringermechanism;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.AudioManager;
import android.widget.Toast;
class MyAlarmReceiver extends BroadcastReceiver{
private AudioManager AM;
@Override
public void onReceive(Context context, Intent intent){
AM.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
Toast.makeText(context, "Ringer Mode changed to Normal", Toast.LENGTH_LONG).show();
}
}

目前，我遇到的问题是，在应用程序启动时，对话框会出现，但按下这两个按钮中的任何一个都会导致崩溃。

Answer 1

您的代码无法工作是因为两个原因：

1. 您的AudioManager为空。将此代码添加到onCreate((：

   mAudioManager=(AudioManager(getSystemService(Context.AUDIO_SERVICE(；

2. 如果你在运行Android Marshmallow或更高版本的设备上进行测试，你需要先请求用户的许可，然后才能设置振铃器模式。您可以通过添加以下代码获得该请求：

   NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M 
   && !notificationManager.isNotificationPolicyAccessGranted()) {
   startActivity(new Intent(Settings.ACTION_NOTIFICATION_POLICY_ACCESS_SETTINGS));
   }
   

Answer 2

Sir如果你在更高版本的android api上测试，你需要先添加询问管理员预览

private void fornougat() {
NotificationManager notificationManager =
(NotificationManager) getSystemService(NOTIFICATION_SERVICE);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N
&& !notificationManager.isNotificationPolicyAccessGranted()) {
Toast.makeText(this, R.string.permission, Toast.LENGTH_SHORT).show();
Intent intent = new Intent(
android.provider.Settings
.ACTION_NOTIFICATION_POLICY_ACCESS_SETTINGS);
startActivity(intent);
}
}