Android java.lang.RuntimeException

Question

好吧，Som首先对我来说是Android编程的新手，它试图做一些非常简单和基本的事情。 一个程序，其中包含各种图片，并取决于您单击哪个按钮显示它。 我没有为我想设置为背景的每张图片创建一个新的xml文件，而是考虑只制作一个xml文件，然后调用它来更改背景。 所以我想使用的是：

public class Picture extends Activity{
@Override

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent=getIntent();
    int picture=intent.getIntExtra("picture", 22);
    ImageView image = (ImageView) findViewById(R.id.pansarvagn);
    image.setBackgroundResource(picture);
    setContentView(R.layout.tmp2);
 }
}

然后我做了这个：

public void displayPicture(int pictureresource){
Intent intent = new Intent();
intent.putExtra("picture", pictureresource);
intent.setClass(getApplicationContext(), Picture.class);
startActivity(intent);
}

最后一个按钮调用看起来像这样：

 ImageView image = (ImageView) findViewById(R.id.pansarvagn);

    Button spgsu8 = (Button) findViewById(R.id.su8);
    spgsu8.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {

    image.setBackgroundResource(R.drawable.su8);
    displayPicture(R.drawable.su8);

然后这是在我的xml文件中，或者我尝试了一堆东西，但是我想调用id并更改图片/背景：

<?xml version="1.0" encoding="utf-8"?>
<ImageView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/su8" android:id="@+id/pansarvagn"></ImageView>

但是无论我如何扭曲，我仍然会提出：

08-30 06:47:07.568: ERROR/AndroidRuntime(449): java.lang.RuntimeException: Unable to start     activity ComponentInfo{com.example.wot/com.example.wot.Picture}: java.lang.NullPointerException
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.os.Looper.loop(Looper.java:123)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at java.lang.reflect.Method.invokeNative(Native Method)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at java.lang.reflect.Method.invoke(Method.java:507)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at dalvik.system.NativeStart.main(Native Method)
08-30 06:47:07.568: ERROR/AndroidRuntime(449): Caused by: java.lang.NullPointerException
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at com.example.wot.Picture.onCreate(Picture.java:17)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-30 06:47:07.568: ERROR/AndroidRuntime(449):     ... 11 more

我希望你们能理解这个：>

Answer 1

尝试下面的代码...我们不能在setcontentview之前定义任何view

public class Picture extends Activity{
@Override

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent=getIntent();
    int picture=intent.getIntExtra("picture", 22);
    setContentView(R.layout.tmp2);  
    ImageView image = (ImageView) findViewById(R.id.pansarvagn);
    image.setBackgroundResource(picture);

 }
}