Question

我正在通过视频教程学习java但我遇到一个奇怪的问题我在java中创建了一个名为OpenedClass的类并实现了两个类。
一个用于OnClickListener，第二个是OnCheckChangeListener但是当我在模拟器上运行应用程序时，它总是给我调用OnClickListener的错误。
我的java类的代码是：

package com.thenewboston.thenewboston;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TextView;

public class OpenedClass extends Activity implements View.OnClickListener,
    OnCheckedChangeListener {

TextView question, test;
Button returnData;
RadioGroup selectionList;
String gotBread;
String setData;
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.send);
    initialize();

private void initialize() {
    // TODO Auto-generated method stub
    question = (TextView) findViewById(R.id.tvQuestion);
    test = (TextView) findViewById(R.id.tvTest);
    returnData = (Button) findViewById(R.id.bResults);
    selectionList = (RadioGroup) findViewById(R.id.rgAnswers);
    selectionList.setOnCheckedChangeListener(this);
    returnData.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    Intent person = new Intent();
    Bundle backpack = new Bundle();
    backpack.putString("answer", setData);
    person.putExtras(backpack);
    setResult(RESULT_OK,person);
    finish();
}

@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
    // TODO Auto-generated method stub
    switch (checkedId) {
    case R.id.rCrazy:
        setData = "Probably Right !";
        break;
    case R.id.rSexy:
        setData = "Definitely Right !"; 
        break;
    case R.id.rBoth:
        setData = "Spot On !";
        break;
    }
    test.setText(setData);
}

}

这是logcat的输出：

01-05 15:59:54.605: E/AndroidRuntime(313): FATAL EXCEPTION: main
01-05 15:59:54.605: E/AndroidRuntime(313): java.lang.RuntimeException: Unable to start        activity   ComponentInfo{com.thenewboston.thenewboston/com.thenewboston.thenewboston.OpenedClass}:   java.lang.NullPointerException
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.os.Looper.loop(Looper.java:123)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.ActivityThread.main(ActivityThread.java:3683)
01-05 15:59:54.605: E/AndroidRuntime(313):  at java.lang.reflect.Method.invokeNative(Native Method)
01-05 15:59:54.605: E/AndroidRuntime(313):  at java.lang.reflect.Method.invoke(Method.java:507)
01-05 15:59:54.605: E/AndroidRuntime(313):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-05 15:59:54.605: E/AndroidRuntime(313):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-05 15:59:54.605: E/AndroidRuntime(313):  at dalvik.system.NativeStart.main(Native Method)
01-05 15:59:54.605: E/AndroidRuntime(313): Caused by: java.lang.NullPointerException
01-05 15:59:54.605: E/AndroidRuntime(313):  at com.thenewboston.thenewboston.OpenedClass.initialize(OpenedClass.java:44)
01-05 15:59:54.605: E/AndroidRuntime(313):  at com.thenewboston.thenewboston.OpenedClass.onCreate(OpenedClass.java:25)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-05 15:59:54.605: E/AndroidRuntime(313):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
01-05 15:59:54.605: E/AndroidRuntime(313):  ... 11 more

左，你们可以看到它告诉我错误在第44行，我的代码中的第44行是

        returnData.setOnClickListener(this);

当我评论这一行时，我根本不理解它，它会告诉我布局，当我不这样做时。知道为什么会这样吗？

Answer 1

来自你的评论marcin_j post

<Button android:id="@+id/bReturn"  // id is bReturn
android:layout_width="wrap_content"
android:layout_height="wrap_content"   
 android:text="Return" >
</Button>

更改此

returnData = (Button) findViewById(R.id.bResults);

到

returnData = (Button) findViewById(R.id.bReturn);

java.lang.runtime异常：无法启动组件

1 个答案: