此活动应该调用另一个活动，但强制关闭应用程序。
package com.example.helloworld;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Data extends Activity implements OnClickListener {
Button start, startFor;
EditText sendET;
TextView gotAnswer;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.get);
initialize();
}
private void initialize() {
// TODO Auto-generated method stub
start = (Button) findViewById(R.id.bSA);
startFor = (Button) findViewById(R.id.bSAFR);
sendET = (EditText) findViewById(R.id.etSend);
gotAnswer = (TextView) findViewById(R.id.tvGot);
start.setOnClickListener(this);
startFor.setOnClickListener(this);
}
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.bSA:
String bread = sendET.getText().toString();
Bundle basket = new Bundle();
basket.putString("key", bread);
Intent a = new Intent(Data.this, OpenedClass.class);
a.putExtras(basket);
startActivity(a);
break;
case R.id.bSAFR:
Intent i = new Intent(Data.this, OpenedClass.class);
startActivityForResult(i,0);
break;
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
}
}
这是要调用的另一个Activity：
package com.example.helloworld;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TextView;
public class OpenedClass extends Activity implements OnClickListener,
OnCheckedChangeListener {
TextView question, test;
Button returnData;
RadioGroup selectionList;
String gotBread, setData;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.send);
initialize();
Bundle gotBasket = getIntent().getExtras();
gotBread = gotBasket.getString("key");
question.setText(gotBread);
}
private void initialize() {
// TODO Auto-generated method stub
question = (TextView) findViewById(R.id.tvQuestions);
test = (TextView) findViewById(R.id.tvText);
returnData = (Button) findViewById(R.id.bResults);
selectionList = (RadioGroup) findViewById(R.id.rgAnswers);
returnData.setOnClickListener(this);
selectionList.setOnCheckedChangeListener(this);
}
public void onClick(View v) {
// TODO Auto-generated method stub
}
public void onCheckedChanged(RadioGroup arg0, int arg1) {
// TODO Auto-generated method stub
switch (arg1) {
case R.id.rChoice1:
setData="ABC";
break;
case R.id.rChoice2:
setData="MNO";
break;
case R.id.rChoice3:
setData="XYZ";
break;
}
test.setText(setData);
}
}
这是我的AndroidMaifest.xml文件：
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.helloworld"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<uses-permission android:name="android.permission.SET_WALLPAPER"/>
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".Splash"
android:label="@string/title_activity_main" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".MainActivity"
android:label="@string/title_activity_main" >
<intent-filter>
</intent-filter>
</activity>
<activity
android:name=".Menu"
android:label="@string/title_activity_main" >
<intent-filter>
<action android:name="com.example.helloworld.MENU" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".TextPlay" android:label="@string/title_activity_main" >
</activity>
<activity
android:name=".Email" android:label="@string/title_activity_main" >
</activity>
<activity
android:name=".Camera" android:label="@string/title_activity_main" android:screenOrientation="portrait" >
</activity>
<activity
android:name=".Data" android:label="@string/title_activity_main" >
</activity>
<activity
android:name=".OpenedClass" android:label="@string/title_activity_main" >
</activity>
</application>
</manifest>
最后LogCat记录：
10-17 10:36:56.423: D/AndroidRuntime(272): Shutting down VM
10-17 10:36:56.423: W/dalvikvm(272): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
10-17 10:36:56.453: E/AndroidRuntime(272): FATAL EXCEPTION: main
10-17 10:36:56.453: E/AndroidRuntime(272): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.helloworld/com.example.helloworld.OpenedClass}: java.lang.NullPointerException
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.os.Handler.dispatchMessage(Handler.java:99)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.os.Looper.loop(Looper.java:123)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-17 10:36:56.453: E/AndroidRuntime(272): at java.lang.reflect.Method.invokeNative(Native Method)
10-17 10:36:56.453: E/AndroidRuntime(272): at java.lang.reflect.Method.invoke(Method.java:521)
10-17 10:36:56.453: E/AndroidRuntime(272): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-17 10:36:56.453: E/AndroidRuntime(272): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-17 10:36:56.453: E/AndroidRuntime(272): at dalvik.system.NativeStart.main(Native Method)
10-17 10:36:56.453: E/AndroidRuntime(272): Caused by: java.lang.NullPointerException
10-17 10:36:56.453: E/AndroidRuntime(272): at com.example.helloworld.OpenedClass.initialize(OpenedClass.java:38)
10-17 10:36:56.453: E/AndroidRuntime(272): at com.example.helloworld.OpenedClass.onCreate(OpenedClass.java:25)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-17 10:36:56.453: E/AndroidRuntime(272): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-17 10:36:56.453: E/AndroidRuntime(272): ... 11 more
10-17 10:36:59.083: I/Process(272): Sending signal. PID: 272 SIG: 9
问题是应用程序编译没有错误，但在我尝试调用活动时崩溃。我不确定问题出在哪里。它是清单吗？
答案 0 :(得分：2)
如果我正确计算了行数（到OpenedClass.java的第38行），NPE就会在这一行生成：
returnData.setOnClickListener(this);
在OpenedClass.initialize()内。变量returnData正在通过以下几行初始化：
returnData = (Button) findViewById(R.id.bResults);
问题很可能是您的布局（send.xml）没有bResults视图，因此returnData被分配null。
答案 1 :(得分：1)
试试这个：
startFor.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.bSA:
String bread = sendET.getText().toString();
Bundle basket = new Bundle();
basket.putString("key", bread);
Intent a = new Intent(Data.this, OpenedClass.class);
a.putExtras(basket);
startActivity(a);
break;
case R.id.bSAFR:
Intent i = new Intent(Data.this, OpenedClass.class);
startActivityForResult(i,0);
break;
}
});
答案 2 :(得分：0)
您已使用此行
a.putExtras(basket);
在第一堂课中并未在OpenedClass
也许这就是问题
答案 3 :(得分：0)
看起来您的某个观点未找到。
调试您的应用并确保它们全部被找到并且不返回null;
答案 4 :(得分：0)
只需在活动中更改
case R.id.bSA:
String bread = sendET.getText().toString();
Intent a = new Intent(Data.this, OpenedClass.class);
a.putExtras("key", bread);
startActivity(a);
break;