我一直在尝试构建我的第一个 Android 应用程序。每次我在模拟器中打开应用程序时，我都会收到一条消息，提示测试已停止工作。这一定是简单的事情。希望你能帮助我。
04-06 15:43:47.806: W/dalvikvm(4275): threadid=1: thread exiting with uncaught exception (group=0xa614d908)
04-06 15:43:47.826: E/AndroidRuntime(4275): FATAL EXCEPTION: main
04-06 15:43:47.826: E/AndroidRuntime(4275): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test/com.test.MainActivity}: java.lang.NullPointerException
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.os.Handler.dispatchMessage(Handler.java:99)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.os.Looper.loop(Looper.java:137)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-06 15:43:47.826: E/AndroidRuntime(4275): at java.lang.reflect.Method.invokeNative(Native Method)
04-06 15:43:47.826: E/AndroidRuntime(4275): at java.lang.reflect.Method.invoke(Method.java:511)
04-06 15:43:47.826: E/AndroidRuntime(4275): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-06 15:43:47.826: E/AndroidRuntime(4275): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-06 15:43:47.826: E/AndroidRuntime(4275): at dalvik.system.NativeStart.main(Native Method)
04-06 15:43:47.826: E/AndroidRuntime(4275): Caused by: java.lang.NullPointerException
04-06 15:43:47.826: E/AndroidRuntime(4275): at com.test.MainActivity.onCreate(MainActivity.java:30)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.Activity.performCreate(Activity.java:5104)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-06 15:43:47.826: E/AndroidRuntime(4275): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
04-06 15:43:47.826: E/AndroidRuntime(4275): ... 11 more
以上是日志文件
public class Main extends ActionBarActivity {
int counter ;
Button add, sub ;
TextView display;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button) findViewById (R.id.bAdd);
sub = (Button) findViewById (R.id.bsub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter --;
display.setText("Your total is " + counter);
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}
以上是主类
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.test.MainActivity$PlaceholderFragment" >
<TextView
android:id="@+id/tvDisplay"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_alignLeft="@+id/bsub"
android:layout_alignParentBottom="true"
android:layout_below="@+id/bsub"
android:gravity="center"
android:text="Your total is 0"
android:textSize="45dp" />
<Button
android:id="@+id/badd"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="16dp"
android:layout_marginTop="78dp"
android:gravity="center"
android:text="Add one"
android:textSize="20dp" />
<Button
android:id="@+id/bsub"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_toRightOf="@+id/badd"
android:layout_centerHorizontal="true"
android:gravity="center"
android:text="Subtract one"
android:textSize="20dp" />
</RelativeLayout>
上面是fragment_main.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.Hello.firstapp.Main"
tools:ignore="MergeRootFrame" />
上面是activity_main.xml
最佳答案
而不是 onCreate()将所有初始化移至 onCreateView()如那些buttons和textview在你 fragment_main.xml这就是为什么你得到 NPE如那些buttons和textview不是 activity_main.xml 的一部分。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
counter = 0;
add = (Button) rootView.findViewById (R.id.bAdd);
sub = (Button) rootView.findViewById (R.id.bsub);
display = (TextView) rootView.findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter --;
display.setText("Your total is " + counter);
}
});
return rootView;
}
关于java - Android应用程序已停止工作-eclipse，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22896682/