我在Android Developer Tools Build的最新版本中遇到了问题：v22.6.2-1085508
在以前的版本只有布局并且还扩展了ActionBarActivity，以前只使用了Activity
，这是非常不同的Java代码：
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.os.Build;
public class MainActivity extends ActionBarActivity implements OnClickListener {
private TextView tv;
private Button btn1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
tv = (TextView) findViewById(R.id.textView1);
// add the listener.
tv.setOnClickListener(this);
// you can define too a listener to your button1.
btn1 = (Button) findViewById(R.id.button1);
btn1.setOnClickListener(this);
}
@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;
}
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.textView1:
tv.setText("hola");
break;
case R.id.button1:
tv.setText("click on button1");
break;
default:
// code..
break;
}
}
}
public class sdfsdsdf {
}
Log Cat：
04-03 07:13:20.305: E/AndroidRuntime(971): FATAL EXCEPTION: main
04-03 07:13:20.305: E/AndroidRuntime(971): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.htapex_ame/com.example.htapex_ame.MainActivity}: java.lang.NullPointerException
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.os.Handler.dispatchMessage(Handler.java:99)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.os.Looper.loop(Looper.java:137)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-03 07:13:20.305: E/AndroidRuntime(971): at java.lang.reflect.Method.invokeNative(Native Method)
04-03 07:13:20.305: E/AndroidRuntime(971): at java.lang.reflect.Method.invoke(Method.java:511)
04-03 07:13:20.305: E/AndroidRuntime(971): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-03 07:13:20.305: E/AndroidRuntime(971): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-03 07:13:20.305: E/AndroidRuntime(971): at dalvik.system.NativeStart.main(Native Method)
04-03 07:13:20.305: E/AndroidRuntime(971): Caused by: java.lang.NullPointerException
04-03 07:13:20.305: E/AndroidRuntime(971): at com.example.htapex_ame.MainActivity.onCreate(MainActivity.java:33)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.Activity.performCreate(Activity.java:5104)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-03 07:13:20.305: E/AndroidRuntime(971): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
04-03 07:13:20.305: E/AndroidRuntime(971): ... 11 more
04-03 07:13:20.315: W/ActivityManager(286): Force finishing activity com.example.htapex_ame/.MainActivity
04-03 07:13:20.325: W/WindowManager(286): Failure taking screenshot for (123x164) to layer 21010
04-03 07:13:20.525: I/Choreographer(286): Skipped 119 frames! The application may be doing too much work on its main thread.
04-03 07:13:20.535: E/SurfaceFlinger(36): ro.sf.lcd_density must be defined as a build property
04-03 07:13:20.715: I/Choreographer(286): Skipped 37 frames! The application may be doing too much work on its main thread.
04-03 07:13:20.745: I/Choreographer(286): Skipped 37 frames! The application may be doing too much work on its main thread.
04-03 07:13:20.845: W/ActivityManager(286): Activity pause timeout for ActivityRecord{40e18340 u0 com.example.htapex_ame/.MainActivity}
04-03 07:13:20.885: D/dalvikvm(405): JIT unchain all for threadid=1
04-03 07:13:20.925: I/Choreographer(286): Skipped 111 frames! The application may be doing too much work on its main thread.
04-03 07:13:20.965: I/Choreographer(286): Skipped 35 frames! The application may be doing too much work on its main thread.
04-03 07:13:21.195: D/dalvikvm(405): GC_FOR_ALLOC freed 1402K, 29% free 4964K/6912K, paused 933ms, total 949ms
04-03 07:13:21.555: I/Choreographer(405): Skipped 362 frames! The application may be doing too much work on its main thread.
04-03 07:13:21.675: I/Choreographer(286): Skipped 32 frames! The application may be doing too much work on its main thread.
04-03 07:13:21.775: I/Choreographer(286): Skipped 41 frames! The application may be doing too much work on its main thread.
04-03 07:13:21.835: I/Choreographer(286): Skipped 33 frames! The application may be doing too much work on its main thread.
04-03 07:13:21.935: I/Choreographer(286): Skipped 39 frames! The application may be doing too much work on its main thread.
04-03 07:13:21.975: D/dalvikvm(405): GC_FOR_ALLOC freed 665K, 30% free 4877K/6912K, paused 333ms, total 335ms
04-03 07:13:22.185: I/Process(971): Sending signal. PID: 971 SIG: 9
xml file fragment_main：
<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.example.htapex_ame.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="19dp"
android:layout_marginTop="36dp"
android:text="Button" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button1"
android:layout_below="@+id/button1"
android:layout_marginTop="20dp"
android:text="TextView" />
</RelativeLayout>
xml文件activity_main：
<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.example.button_a.MainActivity"
tools:ignore="MergeRootFrame" >
</FrameLayout>`
答案 0 :(得分：0)
首先，开发人员工具的新更新没有任何问题。
如果我没有错，你已经发布了片段的xml而不是活动。 如果你想看看你的活动xml，你会发现对应于它的片段的frameLayout。
为此你需要研究片段和所有片段。
此外，您需要将代码放在片段类的onCreateView中。
tv = (TextView) rootView.findViewById(R.id.text View1);
// add the listener.
tv.setOnClickListener(this);
// you can define too a listener to your button1.
btn1 = (Button)rootView.findViewById(R.id.button1);
btn1.setOnClickListener(this);
将TextView和Button设为静态。