如何使用多个 SeekBars (Android) 同时控制多个声音的音量？
How to control the volume of multiple sounds at once using multiple SeekBars (Android)?
如何使用多个SeekBars控制同时播放多个声音的音量？同时播放三个 mp3 文件。一共有三个 SeekBar，每个 Seekbar 的进度应该与它的相关声音文件的音量有关。我遇到的问题是，当我移动一个 SeekBar 时，它会控制所有三种声音的音量。
这是 Android 代码，后面是 XML:
/*
Created by: Justin Clark
Company: VaughnX
Date: June 15 2017
Purpose: To block out external sound using white, brown, and pink noise.
To do: -Increase duration of brown and pink noise files.
-use seek slider as an in-app volume controller
*/
package com.vaughnx.vaugi.soundwall;
import android.app.Activity;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.ToggleButton;
import android.media.MediaPlayer;
import android.media.AudioManager;
public class MainActivity extends Activity {
private SeekBar whiteVolumeSeekBar;
private SeekBar pinkVolumeSeekBar;
private SeekBar brownVolumeSeekBar;
private AudioManager whiteAudioManager;
private AudioManager pinkAudioManager;
private AudioManager brownAudioManager;
private int maxVolume;
private int curVOlume;
final MediaPlayer whiteNoiseMP = MediaPlayer.create(this, R.raw.whitenoise);
final MediaPlayer brownNoiseMP = MediaPlayer.create(this, R.raw.brownnoise);
final MediaPlayer pinkNoiseMP = MediaPlayer.create(this, R.raw.pinknoise);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setVolumeControlStream(AudioManager.STREAM_MUSIC);
initializeSoundController();
initializeVolumeController();
}
//Sets up white, brown, and pink noise players. Uses toggle buttons to turn sound on
//and off.
public void initializeSoundController() {
ToggleButton whiteNoiseToggle = (ToggleButton) findViewById(R.id.whitenoisebutton);
whiteNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
whiteNoiseMP.start();
} else {
// The toggle is disabled
whiteNoiseMP.pause();
}
}
});
ToggleButton brownNoiseToggle = (ToggleButton) findViewById(R.id.brownnoisebutton);
brownNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
brownNoiseMP.start();
} else {
// The toggle is disabled
brownNoiseMP.pause();
}
}
});
ToggleButton pinkNoiseToggle = (ToggleButton) findViewById(R.id.pinknoisebutton);
pinkNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
pinkNoiseMP.start();
} else {
// The toggle is disabled
pinkNoiseMP.pause();
}
}
});
}
//End of sound controller initializations
//Start of control volume with sliders//
private void initializeVolumeController()
{
try{
whiteVolumeSeekBar = (SeekBar) findViewById(R.id.whiteVolumeSeekBar);
whiteVolumeSeekBar.setMax(50);
whiteVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
whiteNoiseMP.setVolume(1-log1, 1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
}
try{
pinkVolumeSeekBar = (SeekBar) findViewById(R.id.pinkVolumeSeekBar);
pinkVolumeSeekBar.setMax(50);
pinkVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
pinkNoiseMP.setVolume(1-log1, 1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
}
try{
brownVolumeSeekBar = (SeekBar) findViewById(R.id.brownVolumeSeekBar);
brownVolumeSeekBar.setMax(50);
brownVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
brownNoiseMP.setVolume(1-log1, 1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
brownVolumeSeekBar.setProgress(25);
} catch (Exception e){
}
//end of volume controller
}}
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
android:background="@drawable/numbsound"
tools:context="com.vaughnx.vaugi.soundwall.MainActivity">
<ToggleButton
android:id="@+id/whitenoisebutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textOff="@string/whiteToggleButton"
android:textOn="@string/whiteToggleButton"
tools:layout_editor_absoluteX="0dp"
tools:layout_editor_absoluteY="247dp"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="16dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<ToggleButton
android:id="@+id/pinknoisebutton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Button"
android:textOff="@string/pinkToggleButton"
android:textOn="@string/pinkToggleButton"
tools:layout_editor_absoluteX="260dp"
tools:layout_editor_absoluteY="247dp"
android:layout_marginTop="48dp"
android:layout_below="@+id/brownnoisebutton"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<ToggleButton
android:id="@+id/brownnoisebutton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_below="@+id/whitenoisebutton"
android:layout_marginTop="44dp"
android:text="Button"
android:textOff="@string/brownToggleButton"
android:textOn="@string/brownToggleButton"
tools:layout_editor_absoluteX="137dp"
tools:layout_editor_absoluteY="247dp" />
<SeekBar
android:id="@+id/whiteVolumeSeekBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/pinknoisebutton"
android:layout_marginTop="62dp" />
<SeekBar
android:id="@+id/brownVolumeSeekBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/whiteVolumeSeekBar"
android:layout_marginTop="62dp" />
<SeekBar
android:id="@+id/pinkVolumeSeekBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/brownVolumeSeekBar"
android:layout_marginTop="62dp" />
</RelativeLayout>
**************************************************************************
LogCat Results:
07-09 17:05:52.621: E/AndroidRuntime(3147): FATAL EXCEPTION: main
07-09 17:05:52.621: E/AndroidRuntime(3147): Process: com.vaughnx.vaugi.soundwall, PID: 3147
07-09 17:05:52.621: E/AndroidRuntime(3147): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.vaughnx.vaugi.soundwall/com.vaughnx.vaugi.soundwall.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3135)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3418)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.access00(ActivityThread.java:231)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1823)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.os.Handler.dispatchMessage(Handler.java:102)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.os.Looper.loop(Looper.java:148)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.main(ActivityThread.java:7422)
07-09 17:05:52.621: E/AndroidRuntime(3147): at java.lang.reflect.Method.invoke(Native Method)
07-09 17:05:52.621: E/AndroidRuntime(3147): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
07-09 17:05:52.621: E/AndroidRuntime(3147): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
07-09 17:05:52.621: E/AndroidRuntime(3147): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.content.ContextWrapper.getResources(ContextWrapper.java:92)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:81)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:549)
您应该使用 MediaPlayer.setVolume 而不是音频管理器来控制音量。
package com.vaughnx.vaugi.soundwall;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.ToggleButton;
import android.media.MediaPlayer;
public class MainActivity extends AppCompatActivity {
private SeekBar whiteVolumeSeekBar;
private SeekBar pinkVolumeSeekBar;
private SeekBar brownVolumeSeekBar;
private int maxVolume;
private int curVOlume;
private MediaPlayer whiteNoiseMP;
private MediaPlayer brownNoiseMP;
private MediaPlayer pinkNoiseMP;
private ToggleButton whiteNoiseToggle;
private ToggleButton brownNoiseToggle;
private ToggleButton pinkNoiseToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Sets up white, brown, and pink noise players. Uses toggle buttons to turn sound on
//and off.
whiteNoiseMP = MediaPlayer.create(MainActivity.this, R.raw.whitenoise);
brownNoiseMP = MediaPlayer.create(MainActivity.this, R.raw.brownnoise);
pinkNoiseMP = MediaPlayer.create(MainActivity.this, R.raw.pinknoise);
whiteNoiseToggle = (ToggleButton) findViewById(R.id.whitenoisebutton);
whiteNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
whiteNoiseMP.start();
} else {
// The toggle is disabled
whiteNoiseMP.pause();
}
}
});
brownNoiseToggle = (ToggleButton) findViewById(R.id.brownnoisebutton);
brownNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
brownNoiseMP.start();
} else {
// The toggle is disabled
brownNoiseMP.pause();
}
}
});
pinkNoiseToggle = (ToggleButton) findViewById(R.id.pinknoisebutton);
pinkNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
pinkNoiseMP.start();
} else {
// The toggle is disabled
pinkNoiseMP.pause();
}
}
});
//End of sound controller initializations
//Start of control volume with sliders//
try{
whiteVolumeSeekBar = (SeekBar) findViewById(R.id.whiteVolumeSeekBar);
whiteVolumeSeekBar.setMax(50);
whiteVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
whiteNoiseMP.setVolume(1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
Log.e("Exception", e.getMessage());
}
try{
pinkVolumeSeekBar = (SeekBar) findViewById(R.id.pinkVolumeSeekBar);
pinkVolumeSeekBar.setMax(50);
pinkVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
pinkNoiseMP.setVolume(1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
Log.e("Exception", e.getMessage());
}
try{
brownVolumeSeekBar = (SeekBar) findViewById(R.id.brownVolumeSeekBar);
brownVolumeSeekBar.setMax(50);
brownVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
brownNoiseMP.setVolume(1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
brownVolumeSeekBar.setProgress(25);
} catch (Exception e){
Log.e("Exception", e.getMessage());
}
//end of volume controller
}
}
我已将最大音量设置为 50，并将起始音量设置为 50%，即 25。
如何使用多个SeekBars控制同时播放多个声音的音量？同时播放三个 mp3 文件。一共有三个 SeekBar，每个 Seekbar 的进度应该与它的相关声音文件的音量有关。我遇到的问题是，当我移动一个 SeekBar 时，它会控制所有三种声音的音量。
这是 Android 代码，后面是 XML:
/*
Created by: Justin Clark
Company: VaughnX
Date: June 15 2017
Purpose: To block out external sound using white, brown, and pink noise.
To do: -Increase duration of brown and pink noise files.
-use seek slider as an in-app volume controller
*/
package com.vaughnx.vaugi.soundwall;
import android.app.Activity;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.ToggleButton;
import android.media.MediaPlayer;
import android.media.AudioManager;
public class MainActivity extends Activity {
private SeekBar whiteVolumeSeekBar;
private SeekBar pinkVolumeSeekBar;
private SeekBar brownVolumeSeekBar;
private AudioManager whiteAudioManager;
private AudioManager pinkAudioManager;
private AudioManager brownAudioManager;
private int maxVolume;
private int curVOlume;
final MediaPlayer whiteNoiseMP = MediaPlayer.create(this, R.raw.whitenoise);
final MediaPlayer brownNoiseMP = MediaPlayer.create(this, R.raw.brownnoise);
final MediaPlayer pinkNoiseMP = MediaPlayer.create(this, R.raw.pinknoise);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setVolumeControlStream(AudioManager.STREAM_MUSIC);
initializeSoundController();
initializeVolumeController();
}
//Sets up white, brown, and pink noise players. Uses toggle buttons to turn sound on
//and off.
public void initializeSoundController() {
ToggleButton whiteNoiseToggle = (ToggleButton) findViewById(R.id.whitenoisebutton);
whiteNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
whiteNoiseMP.start();
} else {
// The toggle is disabled
whiteNoiseMP.pause();
}
}
});
ToggleButton brownNoiseToggle = (ToggleButton) findViewById(R.id.brownnoisebutton);
brownNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
brownNoiseMP.start();
} else {
// The toggle is disabled
brownNoiseMP.pause();
}
}
});
ToggleButton pinkNoiseToggle = (ToggleButton) findViewById(R.id.pinknoisebutton);
pinkNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
pinkNoiseMP.start();
} else {
// The toggle is disabled
pinkNoiseMP.pause();
}
}
});
}
//End of sound controller initializations
//Start of control volume with sliders//
private void initializeVolumeController()
{
try{
whiteVolumeSeekBar = (SeekBar) findViewById(R.id.whiteVolumeSeekBar);
whiteVolumeSeekBar.setMax(50);
whiteVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
whiteNoiseMP.setVolume(1-log1, 1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
}
try{
pinkVolumeSeekBar = (SeekBar) findViewById(R.id.pinkVolumeSeekBar);
pinkVolumeSeekBar.setMax(50);
pinkVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
pinkNoiseMP.setVolume(1-log1, 1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
}
try{
brownVolumeSeekBar = (SeekBar) findViewById(R.id.brownVolumeSeekBar);
brownVolumeSeekBar.setMax(50);
brownVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
brownNoiseMP.setVolume(1-log1, 1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
brownVolumeSeekBar.setProgress(25);
} catch (Exception e){
}
//end of volume controller
}}
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
android:background="@drawable/numbsound"
tools:context="com.vaughnx.vaugi.soundwall.MainActivity">
<ToggleButton
android:id="@+id/whitenoisebutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textOff="@string/whiteToggleButton"
android:textOn="@string/whiteToggleButton"
tools:layout_editor_absoluteX="0dp"
tools:layout_editor_absoluteY="247dp"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="16dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<ToggleButton
android:id="@+id/pinknoisebutton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Button"
android:textOff="@string/pinkToggleButton"
android:textOn="@string/pinkToggleButton"
tools:layout_editor_absoluteX="260dp"
tools:layout_editor_absoluteY="247dp"
android:layout_marginTop="48dp"
android:layout_below="@+id/brownnoisebutton"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<ToggleButton
android:id="@+id/brownnoisebutton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_below="@+id/whitenoisebutton"
android:layout_marginTop="44dp"
android:text="Button"
android:textOff="@string/brownToggleButton"
android:textOn="@string/brownToggleButton"
tools:layout_editor_absoluteX="137dp"
tools:layout_editor_absoluteY="247dp" />
<SeekBar
android:id="@+id/whiteVolumeSeekBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/pinknoisebutton"
android:layout_marginTop="62dp" />
<SeekBar
android:id="@+id/brownVolumeSeekBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/whiteVolumeSeekBar"
android:layout_marginTop="62dp" />
<SeekBar
android:id="@+id/pinkVolumeSeekBar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/brownVolumeSeekBar"
android:layout_marginTop="62dp" />
</RelativeLayout>
**************************************************************************
LogCat Results:
07-09 17:05:52.621: E/AndroidRuntime(3147): FATAL EXCEPTION: main
07-09 17:05:52.621: E/AndroidRuntime(3147): Process: com.vaughnx.vaugi.soundwall, PID: 3147
07-09 17:05:52.621: E/AndroidRuntime(3147): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.vaughnx.vaugi.soundwall/com.vaughnx.vaugi.soundwall.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3135)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3418)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.access00(ActivityThread.java:231)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1823)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.os.Handler.dispatchMessage(Handler.java:102)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.os.Looper.loop(Looper.java:148)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.app.ActivityThread.main(ActivityThread.java:7422)
07-09 17:05:52.621: E/AndroidRuntime(3147): at java.lang.reflect.Method.invoke(Native Method)
07-09 17:05:52.621: E/AndroidRuntime(3147): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
07-09 17:05:52.621: E/AndroidRuntime(3147): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
07-09 17:05:52.621: E/AndroidRuntime(3147): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.content.ContextWrapper.getResources(ContextWrapper.java:92)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:81)
07-09 17:05:52.621: E/AndroidRuntime(3147): at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:549)
您应该使用 MediaPlayer.setVolume 而不是音频管理器来控制音量。
package com.vaughnx.vaugi.soundwall;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.ToggleButton;
import android.media.MediaPlayer;
public class MainActivity extends AppCompatActivity {
private SeekBar whiteVolumeSeekBar;
private SeekBar pinkVolumeSeekBar;
private SeekBar brownVolumeSeekBar;
private int maxVolume;
private int curVOlume;
private MediaPlayer whiteNoiseMP;
private MediaPlayer brownNoiseMP;
private MediaPlayer pinkNoiseMP;
private ToggleButton whiteNoiseToggle;
private ToggleButton brownNoiseToggle;
private ToggleButton pinkNoiseToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Sets up white, brown, and pink noise players. Uses toggle buttons to turn sound on
//and off.
whiteNoiseMP = MediaPlayer.create(MainActivity.this, R.raw.whitenoise);
brownNoiseMP = MediaPlayer.create(MainActivity.this, R.raw.brownnoise);
pinkNoiseMP = MediaPlayer.create(MainActivity.this, R.raw.pinknoise);
whiteNoiseToggle = (ToggleButton) findViewById(R.id.whitenoisebutton);
whiteNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
whiteNoiseMP.start();
} else {
// The toggle is disabled
whiteNoiseMP.pause();
}
}
});
brownNoiseToggle = (ToggleButton) findViewById(R.id.brownnoisebutton);
brownNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
brownNoiseMP.start();
} else {
// The toggle is disabled
brownNoiseMP.pause();
}
}
});
pinkNoiseToggle = (ToggleButton) findViewById(R.id.pinknoisebutton);
pinkNoiseToggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// The toggle is enabled
pinkNoiseMP.start();
} else {
// The toggle is disabled
pinkNoiseMP.pause();
}
}
});
//End of sound controller initializations
//Start of control volume with sliders//
try{
whiteVolumeSeekBar = (SeekBar) findViewById(R.id.whiteVolumeSeekBar);
whiteVolumeSeekBar.setMax(50);
whiteVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
whiteNoiseMP.setVolume(1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
Log.e("Exception", e.getMessage());
}
try{
pinkVolumeSeekBar = (SeekBar) findViewById(R.id.pinkVolumeSeekBar);
pinkVolumeSeekBar.setMax(50);
pinkVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
pinkNoiseMP.setVolume(1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
pinkVolumeSeekBar.setProgress(25);
} catch (Exception e){
Log.e("Exception", e.getMessage());
}
try{
brownVolumeSeekBar = (SeekBar) findViewById(R.id.brownVolumeSeekBar);
brownVolumeSeekBar.setMax(50);
brownVolumeSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
float log1 = (float) (Math.log(50-progress)/Math.log(50));
brownNoiseMP.setVolume(1-log1);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
brownVolumeSeekBar.setProgress(25);
} catch (Exception e){
Log.e("Exception", e.getMessage());
}
//end of volume controller
}
}
我已将最大音量设置为 50，并将起始音量设置为 50%，即 25。