加载到手机后，Android程序崩溃了

Question

如何识别错误？

MainActivity.java

package com.danny;
import com.danny.myfragmentactivity.R;
import android.os.Bundle;
//import android.support.v4.app.FragmentActivity;
import android.support.v7.app.ActionBarActivity;


public class MainActivity extends ActionBarActivity {

    @Override
    public void onCreate (Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState != null) {
            return;
        }

        //try {
            HeadlineFragment headlineFragment=new HeadlineFragment();
            // headlineFragment.setArguments(getIntent().getExtras());
            getFragmentManager().beginTransaction()
                .add(R.id.container, headlineFragment).commit();
        //} 
        //catch (ClassCastException e){
        //    throw new ClassCastException(this.toString()+"error occur in MainActivity Java");
        //}
    }
}

HeadlineFragment.java

Package com.danny;

import com.danny.myfragmentactivity.R;

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class HeadlineFragment extends Fragment {
    private static final CharSequence myText = "hello danny";

    public HeadlineFragment(){}

    @Override
    public void onAttach(Activity activity){
        super.onAttach(activity);
    }
    @Override
    public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View inflaterView=inflater.inflate(R.layout.headline_fragment, container, false);
        return inflaterView;
    }
    @Override
    public void onStart(){
        super.onStart();
        updateActivityDisplay();
    }

void updateActivityDisplay(){
    //try {
        TextView headlineTextView = (TextView) getActivity().findViewById(R.id.headline_fragmentXML);
        headlineTextView.setText(myText);
    //}
    //catch (ClassCastException e) {
    //    throw new ClassCastException (this.toString()+"error in updateActivityDisplay Class");
    //}
    }
}

activity_main.xml中

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.danny.myfragmentactivity.MainActivity"
    tools:ignore="MergeRootFrame" />

headline_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<Textview xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/headline_fragmentXML"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/green"
    ></Textview>

LogCat文件

05-23 14:36:03.476: D/AndroidRuntime(5503): Shutting down VM
05-23 14:36:03.476: W/dalvikvm(5503): threadid=1: thread exiting with uncaught exception (group=0x4144a2a0)
05-23 14:36:03.476: E/AndroidRuntime(5503): FATAL EXCEPTION: main
05-23 14:36:03.476: E/AndroidRuntime(5503): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.danny.myfragmentactivity/com.danny.myfragmentactivity.MainActivity}: java.lang.ClassNotFoundException: com.danny.myfragmentactivity.MainActivity
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2034)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.ActivityThread.access$700(ActivityThread.java:140)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.os.Looper.loop(Looper.java:137)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.ActivityThread.main(ActivityThread.java:4935)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at java.lang.reflect.Method.invokeNative(Native Method)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at java.lang.reflect.Method.invoke(Method.java:511)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at dalvik.system.NativeStart.main(Native Method)
05-23 14:36:03.476: E/AndroidRuntime(5503): Caused by: java.lang.ClassNotFoundException: com.danny.myfragmentactivity.MainActivity
05-23 14:36:03.476: E/AndroidRuntime(5503):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
05-23 14:36:03.476: E/AndroidRuntime(5503):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2025)
05-23 14:36:03.476: E/AndroidRuntime(5503):     ... 11 more
05-23 14:36:15.007: I/Process(5503): Sending signal. PID: 5503 SIG: 9

Answer 1

创建inflaterView全局变量并使用它而不是getActivity（）。

View inflaterView;

@Override
    public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        inflaterView=inflater.inflate(R.layout.headline_fragment, container, false);
        return inflaterView;
    }

void updateActivityDisplay(){

    TextView headlineTextView = (TextView) inflaterView.findViewById(R.id.headline_fragmentXML);
    headlineTextView.setText(myText);


    }

Answer 2

使用getSupportFragmentManager代替getFragmentManager。

Answer 3

java.lang.ClassNotFoundException: com.danny.myfragmentactivity.MainActivity

当您的清单文件显示在MainActivity时，您的com.danny位于包com.danny.myfragmentactivity中。确保清单和代码一致。