Android完成子活动错误
我正在做一个项目,在这个项目中,我需要在Tabhost的一个选项卡下放置一些活动。我正在使用自定义Android完成子活动错误,android,android-activity,childactivity,Android,Android Activity,Childactivity,我正在做一个项目,在这个项目中,我需要在Tabhost的一个选项卡下放置一些活动。我正在使用自定义tabgroupactivity示例,这是我在互联网上找到的,但现在我在完成活动时遇到了一点问题。首先,这里是自定义类代码: import java.util.ArrayList; import android.app.Activity; import android.app.ActivityGroup; import android.app.LocalActivityManager; impo
tabgroupactivity
示例,这是我在互联网上找到的,但现在我在完成活动时遇到了一点问题。首先,这里是自定义类代码:
import java.util.ArrayList;
import android.app.Activity;
import android.app.ActivityGroup;
import android.app.LocalActivityManager;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Window;
/*
* The purpose of this Activity is to manage the activities in a tab.
* Note: Child Activities can handle Key Presses before they are seen here.
* @author Eric Harlow
*/
public class TabGroupActivity extends ActivityGroup {
private ArrayList<String> mIdList;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (mIdList == null) mIdList = new ArrayList<String>();
}
/*
* This is called when a child activity of this one calls its finish method.
* This implementation calls {@link LocalActivityManager#destroyActivity} on the child activity
* and starts the previous activity.
* If the last child activity just called finish(),this activity (the parent),
* calls finish to finish the entire group.
*/
@Override
public void finishFromChild(Activity child) {
LocalActivityManager manager = getLocalActivityManager();
int index = mIdList.size()-1;
if(index < 1) {
finish();
return;
}
manager.destroyActivity(mIdList.get(index), true);
mIdList.remove(index);
index--;
String lastId = mIdList.get(index);
Intent lastIntent = manager.getActivity(lastId).getIntent();
Window newWindow = manager.startActivity(lastId, lastIntent);
setContentView(newWindow.getDecorView());
}
/*
* Starts an Activity as a child Activity to this.
* @param Id Unique identifier of the activity to be started.
* @param intent The Intent describing the activity to be started.
* @throws android.content.ActivityNotFoundException.
*/
public void startChildActivity(String Id, Intent intent) {
Window window = getLocalActivityManager().startActivity(Id,intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
if (window != null) {
mIdList.add(Id);
setContentView(window.getDecorView());
}
}
/*
* The primary purpose is to prevent systems before android.os.Build.VERSION_CODES.ECLAIR
* from calling their default KeyEvent.KEYCODE_BACK during onKeyDown.
*/
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
//preventing default implementation previous to android.os.Build.VERSION_CODES.ECLAIR
return true;
}
return super.onKeyDown(keyCode, event);
}
/*
* Overrides the default implementation for KeyEvent.KEYCODE_BACK
* so that all systems call onBackPressed().
*/
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
onBackPressed();
return true;
}
return super.onKeyUp(keyCode, event);
}
/*
* If a Child Activity handles KeyEvent.KEYCODE_BACK.
* Simply override and add this method.
*/
@Override
public void onBackPressed () {
int length = mIdList.size();
if ( length >=1) {
Activity current = getLocalActivityManager().getActivity(mIdList.get(length-1));
current.finish();
}
}
}
我是这样开始的:
Intent previewMessage = new Intent(A.this, C.class);
previewMessage.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
TabGroupActivity parentActivity = (TabGroupActivity)getParent();
parentActivity.startChildActivity("ExpectSoon", previewMessage);
这里是问题:当我启动几次a、B、C
时,比如a-->B-->C-->B-->C-->a-->C
等。没有问题……但当我按下后退按钮时,我从标记组活动中获得了此行的NullPointerException:
Intent lastIntent = manager.getActivity(lastId).getIntent();
这是LogCat的输出:
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): java.lang.NullPointerException
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.stampii.stampii.TabGroupActivity.finishFromChild(TabGroupActivity.java:49)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.app.Activity.finish(Activity.java:3420)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.stampii.stampii.TabGroupActivity.onBackPressed(TabGroupActivity.java:104)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.stampii.stampii.TabGroupActivity.onKeyUp(TabGroupActivity.java:89)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.KeyEvent.dispatch(KeyEvent.java:1527)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.app.Activity.dispatchKeyEvent(Activity.java:2210)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1779)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:811)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:811)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:811)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.widget.TabHost.dispatchKeyEvent(TabHost.java:278)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:811)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:811)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1812)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1160)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.app.Activity.dispatchKeyEvent(Activity.java:2205)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1779)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewRoot.deliverKeyEventToViewHierarchy(ViewRoot.java:2758)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2730)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.view.ViewRoot.handleMessage(ViewRoot.java:1999)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.os.Handler.dispatchMessage(Handler.java:99)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.os.Looper.loop(Looper.java:150)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at android.app.ActivityThread.main(ActivityThread.java:4293)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at java.lang.reflect.Method.invokeNative(Native Method)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at java.lang.reflect.Method.invoke(Method.java:507)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
10-05 10:51:30.995: ERROR/AndroidRuntime(20377): at dalvik.system.NativeStart.main(Native Method)
有什么办法解决这个问题吗?我想你得这样开始
Intent intent = new Intent(A.this,B.class);
TabGroupActivity parent=(TabGroupActivity)getParent();
parent.startChildActivity("msg",intent);
我想你必须这样开始
Intent intent = new Intent(A.this,B.class);
TabGroupActivity parent=(TabGroupActivity)getParent();
parent.startChildActivity("msg",intent);
我也有同样的问题 但经过调试,我才知道这条线
parentActivity.startChildActivity(STRING_ID, intent);
负责NullPointerException
这是因为,您可能使用相同的STRING\u ID
来启动多个子活动。因此,当按下on后,带有STRING\u ID
的意图将从列表中删除
调用startChildActivity
的方法是
parentActivity.startChildActivity(UNIQUE_STRING_ID, intent);
UNIQUE\u STRING\u ID
必须不同我遇到了同样的问题
但经过调试,我才知道这条线
parentActivity.startChildActivity(STRING_ID, intent);
负责NullPointerException
这是因为,您可能使用相同的STRING\u ID
来启动多个子活动。因此,当按下on后,带有STRING\u ID
的意图将从列表中删除
调用startChildActivity
的方法是
parentActivity.startChildActivity(UNIQUE_STRING_ID, intent);
UNIQUE\u STRING\u ID
必须是不同的检查manager.getActivity(lastId).getIntent()是否为null?????是的,这就是为什么在那一行给我一个NullpointerException,但我不知道如何修复它,这就是为什么我在这里问这个问题NullPointer异常从未抛出,因为您访问空对象或空变量,并且代码中需要它的值,所以…我正在研究这个错误,但是当这个错误发生时??当你调用此活动时,你的意图可能是错误的开始活动…我在开始按后退按钮时出错…不是第一次。实际上,我想清除这些活动的历史记录,当我按活动C或B或A上的后退按钮时,我想完成父活动。但现在,当我按后退按钮时,它是错误的返回到上一个活动(A->B),当我再次按下它时,它崩溃了。我试图修改finishFromChild
方法,但它不起作用。天哪!!!onbackpressed()是当您按下back按钮时调用的方法…所以编写此方法并尝试调用intent,,,,,,,,,以及完成当前活动………检查manager.getActivity(lastId)。getIntent()是否为null?????是的,这就是为什么在那一行上会向我抛出一个NullpointerException,但我不知道如何修复它,这就是为什么我在这里问这个问题NullPointer异常从未抛出,因为您访问空对象或空变量,并且代码中需要它的值,所以…我正在研究这个错误,但是当这个错误发生时??当你调用此活动时,你的意图可能是错误的开始活动…我在开始按后退按钮时出错…不是第一次。实际上,我想清除这些活动的历史记录,当我按活动C或B或A上的后退按钮时,我想完成父活动。但现在,当我按后退按钮时,它是错误的返回到上一个活动(A->B),当我再次按下它时,它崩溃了。我试图修改finishFromChild
方法,但它不起作用。天哪!!!onbackpressed()是当您按back按钮时调用的方法…因此,编写此方法并尝试调用intent,,,,,,,,,以及完成当前活动………我得到相同的异常,因此设置标志与否并不重要。我得到相同的异常,因此,我是否设置标志并不重要。谢谢。我使用STRING_ID作为系统当前时间,单位为millisecond.tabgroup.startChildActivity(“+system.currentTimeMillis(),I”);谢谢。我使用字符串_ID作为系统当前时间,单位为millisecond.tabgroup.startChildActivity(“+system.currentTimeMillis(),i”);