我有以下活动：
package com.example.myapp;
import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.SharedPreferences;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.animation.Animation;
import android.view.animation.Animation.AnimationListener;
import android.view.animation.AnimationUtils;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ScrollView;
import android.widget.Toast;
public class HomeActivity extends Activity implements AnimationListener {
// Animation
Animation animFadein;
Animation animFadeout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home_start);
// load the animation
animFadein = AnimationUtils.loadAnimation(getApplicationContext(),R.anim.fade_in);
animFadeout = AnimationUtils.loadAnimation(getApplicationContext(),R.anim.fade_out);
// set animation listener
animFadein.setAnimationListener(this);
ImageButton homepage =(ImageButton)findViewById(R.id.homepage);
ImageButton new_b =(ImageButton)findViewById(R.id.new_b);
ImageButton view_b =(ImageButton)findViewById(R.id.view_b);
ImageButton home_b =(ImageButton)findViewById(R.id.home_b);
ImageButton info_b =(ImageButton)findViewById(R.id.info_b);
Button back_b =(Button)findViewById(R.id.back_b);
Button site =(Button)findViewById(R.id.site);
homepage.startAnimation(animFadein);
//Click on screen to start
homepage.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
View homepage = (View)findViewById(R.id.homepage);
View startpage = (View)findViewById(R.id.startpage);
homepage.setVisibility(View.GONE);
homepage.startAnimation(animFadeout);
startpage.setVisibility(View.VISIBLE);
startpage.setAnimation(animFadein);};});
new_b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences values = getSharedPreferences("valoar", 0);
SharedPreferences.Editor editor = values.edit();
editor.clear();
editor.commit();
View startpage = (View)findViewById(R.id.startpage);
startpage.setAnimation(animFadeout);
Intent intent = new Intent(HomeActivity.this,QuestionsActivity.class);
startActivity(intent);}});
home_b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
View homepage = (View)findViewById(R.id.homepage);
View startpage = (View)findViewById(R.id.startpage);
homepage.setVisibility(View.VISIBLE);
homepage.startAnimation(animFadein);
startpage.startAnimation(animFadeout);
startpage.setVisibility(View.GONE);};});
info_b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
View startpage = (View)findViewById(R.id.startpage);
View infopage = (View)findViewById(R.id.infopage);
ScrollView info_s = (ScrollView)findViewById(R.id.info_s);
infopage.setVisibility(View.VISIBLE);
info_s.setVisibility(View.VISIBLE);
infopage.startAnimation(animFadein);
startpage.startAnimation(animFadeout);
startpage.setVisibility(View.GONE);};});
back_b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
View startpage = (View)findViewById(R.id.startpage);
View infopage = (View)findViewById(R.id.infopage);
ScrollView info_s = (ScrollView)findViewById(R.id.info_s);
infopage.setVisibility(View.GONE);
info_s.setVisibility(View.GONE);
infopage.startAnimation(animFadeout);
startpage.startAnimation(animFadein);
startpage.setVisibility(View.VISIBLE);};});
**site.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent internetIntent = new Intent(Intent.ACTION_VIEW,
Uri.parse("http://www.i-amapp.com"));
internetIntent.setComponent(new ComponentName("com.android.browser","com.android.browser.BrowserActivity"));
internetIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(internetIntent);};});**
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.home, menu);
return true;
}
@Override
public void onAnimationEnd(Animation arg0) {
// TODO Auto-generated method stub
}
@Override
public void onAnimationRepeat(Animation animation) {
// TODO Auto-generated method stub
}
@Override
public void onAnimationStart(Animation animation) {
// TODO Auto-generated method stub
}
/**
* Back button listener.
* Will close the application if the back button pressed twice.
*/
@Override
public void onBackPressed()
{
int backButtonCount = 0;
if(backButtonCount >= 1)
{
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
finish();
}
else
{
Toast.makeText(this, "Press the x button to close the application.", Toast.LENGTH_SHORT).show();
backButtonCount++;
}
}
}
它在android 4.1.2中工作得非常好，但是在android 2.3.7中它崩溃了，而Logcat显示：
D/AndroidRuntime(2172): Shutting down VM
W/dalvikvm(2172): threadid=1: thread exiting with uncaught exception (group=0x40018560)
E/AndroidRuntime(2172): FATAL EXCEPTION: main
E/AndroidRuntime(2172): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapp/com.example.myapp.HomeActivity}: java.lang.NullPointerException
E/AndroidRuntime(2172): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768)
E/AndroidRuntime(2172): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784)
E/AndroidRuntime(2172): at android.app.ActivityThread.access$1500(ActivityThread.java:123)
E/AndroidRuntime(2172): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939)
E/AndroidRuntime(2172): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(2172): at android.os.Looper.loop(Looper.java:130)
E/AndroidRuntime(2172): at android.app.ActivityThread.main(ActivityThread.java:3835)
E/AndroidRuntime(2172): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(2172): at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime(2172): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:864)
E/AndroidRuntime(2172): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:622)
E/AndroidRuntime(2172): at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(2172): Caused by: java.lang.NullPointerException
E/AndroidRuntime(2172): at com.example.myapp.HomeActivity.onCreate(HomeActivity.java:107)
E/AndroidRuntime(2172): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
E/AndroidRuntime(2172): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
E/AndroidRuntime(2172): ... 11 more
D/dalvikvm(3117): GC_EXTERNAL_ALLOC freed 61K, 50% free 2724K/5379K, external 0K/0K, paused 44ms
D/dalvikvm(3117): GC_EXTERNAL_ALLOC freed 4K, 50% free 2730K/5379K, external 507K/513K, paused 43ms
D/dalvikvm(3117): GC_EXTERNAL_ALLOC freed 1K, 50% free 2736K/5379K, external 1068K/1524K, paused 43ms
D/dalvikvm(3117): GC_EXTERNAL_ALLOC freed 1K, 50% free 2741K/5379K, external 1669K/2086K, paused
这就是logcat显示的全部内容。我无法弄清问题是什么！ 为什么它在android 2.3中崩溃？