Question

private void swapLayouts(final int currentLayoutId, final int requestedLayout) {

    View layout = (View) this.findViewById(currentLayoutId);
    ViewGroup parent = (ViewGroup) layout.getParent();
    int index = parent.indexOfChild(layout);

    parent.removeView(layout);
    layout = getLayoutInflater().inflate(requestedLayout, parent, false);

    parent.addView(layout, index);
}

NullPointerException抛出ViewGroup parent = (ViewGroup) layout.getParent();

这是LogCat输出：

09-30 19:04:34.465: E/AndroidRuntime(4059): FATAL EXCEPTION: main
09-30 19:04:34.465: E/AndroidRuntime(4059): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.blah.blah/com.blah.blah.VideoActivity}: java.lang.NullPointerException    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.ActivityThread.access$600(ActivityThread.java:141)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.os.Handler.dispatchMessage(Handler.java:99)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.os.Looper.loop(Looper.java:137)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.ActivityThread.main(ActivityThread.java:5103)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at java.lang.reflect.Method.invokeNative(Native Method)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at java.lang.reflect.Method.invoke(Method.java:525)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at dalvik.system.NativeStart.main(Native Method)    
09-30 19:04:34.465: E/AndroidRuntime(4059): Caused by: java.lang.NullPointerException    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at com.blah.blah.VideoActivity.swapLayouts(VideoActivity.java:287)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at com.blah.blah.VideoActivity.onCreate(VideoActivity.java:75)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.Activity.performCreate(Activity.java:5133)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)    
09-30 19:04:34.465: E/AndroidRuntime(4059):     ... 11 more

Answer 1

根据文档，如果此视图是嵌入式子级，则getParent（）将返回父视图。

View是嵌入式儿童吗？如果没有，getParent（）将返回null。

Answer 2

它与Android版本无关，而是与不同的布局文件夹无关。

检查所有xml变种文件的ID。

您在java代码中调用R.id. *使用的所有ID都应该在同一个xml文件的所有变体中定义。

查看 - ＆gt; getParent（）在Android 2.3中工作正常但在Android 4+中抛出NullPointerException

2 个答案: