在按下激活单选按钮所在 xml 的按钮后，我的应用程序崩溃了。
logcat 说我的错误是 java.lang.nullpointerexception。
我已经包含了我的 logcat、发生错误的 java 和 list 。
我最初的 RadioButtons 出现了问题，程序允许我同时选中它们，但无法取消选中它们。当我更改编码以包含 onCheckChange 监听器时，只要我按下 RadioButton，应用程序就会崩溃。
07-17 18:09:37.067: W/dalvikvm(329): threadid=1: thread exiting with uncaught exception (group=0x40015560)
07-17 18:09:37.077: E/AndroidRuntime(329): FATAL EXCEPTION: main
07-17 18:09:37.077: E/AndroidRuntime(329): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.com.proto1/com.example.com.proto1.Voiceprompt}: java.lang.ClassNotFoundException: com.example.com.proto1.Voiceprompt in loader dalvik.system.PathClassLoader[/data/app/com.example.com.proto1-2.apk]
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.os.Handler.dispatchMessage(Handler.java:99)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.os.Looper.loop(Looper.java:123)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.ActivityThread.main(ActivityThread.java:3683)
07-17 18:09:37.077: E/AndroidRuntime(329): at java.lang.reflect.Method.invokeNative(Native Method)
07-17 18:09:37.077: E/AndroidRuntime(329): at java.lang.reflect.Method.invoke(Method.java:507)
07-17 18:09:37.077: E/AndroidRuntime(329): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-17 18:09:37.077: E/AndroidRuntime(329): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-17 18:09:37.077: E/AndroidRuntime(329): at dalvik.system.NativeStart.main(Native Method)
07-17 18:09:37.077: E/AndroidRuntime(329): Caused by: java.lang.ClassNotFoundException: com.example.com.proto1.Voiceprompt in loader dalvik.system.PathClassLoader[/data/app/com.example.com.proto1-2.apk]
07-17 18:09:37.077: E/AndroidRuntime(329): at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
07-17 18:09:37.077: E/AndroidRuntime(329): at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
07-17 18:09:37.077: E/AndroidRuntime(329): at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
07-17 18:09:37.077: E/AndroidRuntime(329): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)
07-17 18:09:37.077: E/AndroidRuntime(329): ... 11 more
package com.example.com.proto1;
import android.app.Activity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
public class VoicePrompts extends Activity implements OnCheckedChangeListener {
RadioButton on, off, onc, offc;
// Button Sound
MediaPlayer buttonSound1 = MediaPlayer.create(VoicePrompts.this, R.raw.vpo);
MediaPlayer buttonSound2 = MediaPlayer
.create(VoicePrompts.this, R.raw.vpof);
MediaPlayer buttonSound3 = MediaPlayer
.create(VoicePrompts.this, R.raw.vpoc);
MediaPlayer buttonSound4 = MediaPlayer.create(VoicePrompts.this,
R.raw.vpofc);
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.voiceprompts);
// Setting up the button references
on = (RadioButton) findViewById(R.id.vbutton1);
off = (RadioButton) findViewById(R.id.vbutton2);
onc = (RadioButton) findViewById(R.id.vbutton1);
offc = (RadioButton) findViewById(R.id.vbutton2);
buttonSound1 = MediaPlayer.create(VoicePrompts.this, R.raw.vpo);
buttonSound2 = MediaPlayer.create(VoicePrompts.this, R.raw.vpof);
buttonSound3 = MediaPlayer.create(VoicePrompts.this, R.raw.vpoc);
buttonSound4 = MediaPlayer.create(VoicePrompts.this, R.raw.vpofc);
}
public void onCheckedChanged(RadioGroup arg0, int checkedId) {
// TODO Auto-generated method stub
switch (checkedId) {
case R.id.vbutton1:
on.setOnLongClickListener(new View.OnLongClickListener() {
public boolean onLongClick(View v) {
// TODO Auto-generated method stub
try {
buttonSound1.prepare();
buttonSound1.start();
startActivity(new Intent("android.intent.action.VPON"));
} catch (Exception e) {
}
return false;
}
});
onc.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
try {
buttonSound3.prepare();
buttonSound3.start();
startActivity(new Intent("android.intent.action.VPON"));
} catch (Exception e) {
}
;
}
});
break;
case R.id.vbutton2:
off.setOnLongClickListener(new View.OnLongClickListener() {
public boolean onLongClick(View v) {
// TODO Auto-generated method stub
try {
buttonSound2.prepare();
buttonSound2.start();
startActivity(new Intent("android.intent.action.VPOFF"));
} catch (Exception e) {
}
;
return false;
}
});
offc.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
try {
buttonSound4.prepare();
buttonSound4.start();
startActivity(new Intent("android.intent.action.VPOFF"));
} catch (Exception e) {
}
;
}
});
break;
}
}
}
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.com.proto1"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".mainj"
android:label="@string/title_activity_mainj" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".menu"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MENU" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".Infoactive"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.INFOSCREEN" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".VoicePrompts"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.VOICEPROMPTS" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".VPon"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.VPON" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".VPoff"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.VPOFF" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
package com.example.com.proto1;
import android.app.Activity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class menu extends Activity {
@Override
protected void onCreate(Bundle aboutmenu) {
// TODO Auto-generated method stub
super.onCreate(aboutmenu);
setContentView(R.layout.mainx);
// Button Sound
final MediaPlayer buttonSound = MediaPlayer.create(menu.this,
R.raw.button_click);
// Setting up the button references
Button info = (Button) findViewById(R.id.aboutbutton);
Button voice = (Button) findViewById(R.id.voicebutton);
info.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
buttonSound.start();
startActivity(new Intent("android.intent.action.INFOSCREEN"));
}
});
voice.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
buttonSound.start();
Intent voiceIntent = new Intent("android.intent.action.VOICEPROMPTS");
startActivity(voiceIntent);
}
});
}
}
最佳答案
在setContentView(R.layout.voiceprompts);之后给出按钮引用
喜欢，
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.voiceprompts);
// Setting up the button references
on = (RadioButton) findViewById(R.id.vbutton1);
off = (RadioButton) findViewById(R.id.vbutton2);
onc = (RadioButton) findViewById(R.id.vbutton1);
offc = (RadioButton) findViewById(R.id.vbutton2);
}
关于android - java.lang.nullpointerException错误: app crashes，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11543917/