我很久以前使用 TabActivity 和 ActivityGroup（现已弃用）创建了一个项目。
问题可能很简单，但首先我想澄清一下流程。我的 Tabhost 中有 4 个标签。我使用以下代码来跟踪活动回栈。
MyActivityGroup.java
public class MyActivityGroup extends ActivityGroup {
public static Stack<String> stack;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (stack == null) {
stack = new Stack<String>();
}
push("1stStackActivity", new Intent(this, Home.class));
}
@Override
public void finishFromChild(Activity child) {
pop();
}
@Override
public void onBackPressed() {
pop();
}
public void push(String id, Intent intent) {
Window window = getLocalActivityManager().startActivity(id,
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
if (window != null) {
stack.push(id);
setContentView(window.getDecorView());
}
}
public void pop() {
if (stack.size() == 1) {
finish();
}
LocalActivityManager manager = getLocalActivityManager();
manager.destroyActivity(stack.pop(), true);
if (stack.size() > 0) {
Intent lastIntent = manager.getActivity(stack.peek()).getIntent()
.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
Window newWindow = manager.startActivity(stack.peek(), lastIntent);
setContentView(newWindow.getDecorView());
}
}
}
注意这里：
push("1stStackActivity", new Intent(this, Home.class));
Home.class 是我第一个加载到我的HOME TAB.
这是一张图片，它也显示了我的流程和问题。
从Activity A我点击一个按钮开始（通过查看图 Activity A 浏览）。我开始这样的新活动
Intent intent = new Intent();
intent.setClass(getParent(), BookOverView.class);
MyActivityGroup activityStack = (MyActivityGroup) getParent();
activityStack.push("2ndStackActivity", intent);
Activity B这在电流上加载我HOME TAB也将活动推入堆栈。
从活动 B 当我单击任何列表项时，我将在同一个选项卡中使用与上面相同的代码开始一个新活动(3rdStackActivity)。它开始了我的Activity c; 当我按回 KEY 时，它工作正常（即来自 "Activity C" --> "ACTIVITY B" --> ACTIVITY A ）。
问题
站立时，activity C当我单击Home TAB（参见图活动 C）时，它应该回到我的第一个活动（即活动 A）。
这是我的HOME TAB点击事件
getTabWidget().getChildAt(0).setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (getTabHost().getCurrentTab() == 0) {
\\ Check If stack has at least more then one activity loaded.
if (MyActivityGroup.stack.size() > 1) {
//My code to clear the stack and load the 1st Activity goes here
// I tried Here to clear my stack
// But not sccessfull
}
} else {
getTabHost().setCurrentTab(0);
}
}
});
我在尝试清除堆栈并开始第一个家庭课程时遇到问题。
这是我的 MainActivity.java，它扩展了 TabActivity
public class MainActivity extends TabActivity {
Context context = MainActivity.this;
TabHost tabHost;
TabSpec spec;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tabHost = getTabHost();
// Android tab
tabHost.addTab(tabHost
.newTabSpec("Home")
.setIndicator("Home",
getResources().getDrawable(R.drawable.home))
.setContent(
new Intent(this, MyActivityGroup.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));
tabHost.addTab(tabHost
.newTabSpec("Now Reading")
.setIndicator("Now Reading",
getResources().getDrawable(R.drawable.now_reading))
.setContent(
new Intent(this, NowReadingActivityGroup.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));
tabHost.addTab(tabHost
.newTabSpec("Favorites")
.setIndicator("Favorites",
getResources().getDrawable(R.drawable.favorites))
.setContent(
new Intent(this, FavoriteActivityGroup.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));
tabHost.addTab(tabHost
.newTabSpec("Profile")
.setIndicator("Profile",
getResources().getDrawable(R.drawable.profile))
.setContent(
new Intent(this, ProfileActivityGroup.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));
tabHost.setCurrentTabByTag("Home");
tabHost.setOnTabChangedListener(new OnTabChangeListener() {
@Override
public void onTabChanged(String tabId) {
Toast.makeText(context, "Changed", Toast.LENGTH_SHORT).show();
}
});
}
@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
getTabWidget().getChildAt(0).setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (getTabHost().getCurrentTab() == 0) {
if (MyActivityGroup.stack.size() > 1) {
}
} else {
getTabHost().setCurrentTab(0);
}
}
});
}
}
编辑 2
我在我的 onTabClick 事件中这样做了
if (MyActivityGroup.stack.size() > 1) {
while (!MyActivityGroup.stack.isEmpty()) {
MyActivityGroup.stack.pop();
}
Intent homeIntent = new Intent();
homeIntent.setClass(MainActivity.this, Home.class);
MyActivityGroup activityStack = (MyActivityGroup) getCurrentActivity();
activityStack.push("HomeActivity", homeIntent);
}
} else {
getTabHost().setCurrentTab(0);
}
这会加载我的第一个活动并清除我的活动堆栈。但问题是，现在每当将我的选项卡更改为任何其他选项卡并返回主选项卡并按返回按钮时，它都会崩溃。这是日志猫。
05-31 14:15:42.769: E/AndroidRuntime(550): FATAL EXCEPTION: main
05-31 14:15:42.769: E/AndroidRuntime(550): java.lang.NullPointerException
05-31 14:15:42.769: E/AndroidRuntime(550): at my.islamic.books.lib.app.MyActivityGroup.pop(MyActivityGroup.java:120)
05-31 14:15:42.769: E/AndroidRuntime(550): at my.islamic.books.lib.app.MyActivityGroup.finishFromChild(MyActivityGroup.java:30)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.Activity.finish(Activity.java:3259)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.Activity.onBackPressed(Activity.java:1920)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.Activity.onKeyUp(Activity.java:1898)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.KeyEvent.dispatch(KeyEvent.java:1280)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.Activity.dispatchKeyEvent(Activity.java:2078)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1663)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1687)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1120)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.Activity.dispatchKeyEvent(Activity.java:2073)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1663)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.widget.TabHost.dispatchKeyEvent(TabHost.java:278)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:789)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1687)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1120)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.Activity.dispatchKeyEvent(Activity.java:2073)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1663)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewRoot.deliverKeyEventToViewHierarchy(ViewRoot.java:2560)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2535)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.view.ViewRoot.handleMessage(ViewRoot.java:1867)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.os.Handler.dispatchMessage(Handler.java:99)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.os.Looper.loop(Looper.java:123)
05-31 14:15:42.769: E/AndroidRuntime(550): at android.app.ActivityThread.main(ActivityThread.java:3683)
05-31 14:15:42.769: E/AndroidRuntime(550): at java.lang.reflect.Method.invokeNative(Native Method)
05-31 14:15:42.769: E/AndroidRuntime(550): at java.lang.reflect.Method.invoke(Method.java:507)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-31 14:15:42.769: E/AndroidRuntime(550): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-31 14:15:42.769: E/AndroidRuntime(550): at dalvik.system.NativeStart.main(Native Method)