进度条一直显示不消失
在程序中使用进度条，但是出现这个情况：进度条一直显示很久很久都不消失。在程序中使用显示和隐藏进度条的代码片段如下所示
public void showProgressDialog(String msg) {
if(progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
progressDialog = null;
}
progressDialog = ProgressDialog.show(context, "", msg);
}
public void hideProgressDialog() {
if(progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
progressDialog = null;
}
}在程序中调用以上方法的代码片段是
@Override
public void onRequestStarted(int requestCode) {
switch(requestCode) {
case REQUEST_GET_TJ:
showProgressDialog("正在加载数据，请稍等...");
break;
}
}
@Override
public void onRequestFinished(int requestCode, int resultCode, IVideoResult result) {
switch(requestCode) {
case REQUEST_GET_TJ:
hideProgressDialog();
processGetTJ(resultCode, result);
break;
}
}在Fragment嵌套Fragment时出现以下错误
Binary XML file line #49: Duplicate id 0x7f070071, tag null, or parent id 0x0 with another fragment for com.tvie.ivideo.pad.main.HotVideoFragment
11-18 11:33:45.851: E/AndroidRuntime(8376): android.view.InflateException: Binary XML file line #49: Error inflating class fragment 11-18 11:33:45.851: E/AndroidRuntime(8376): Caused by: java.lang.IllegalArgumentException: Binary XML file line #49: Duplicate id 0x7f070071, tag null, or parent id 0x0 with another fragment for com.tvie.ivideo.pad.main.HotVideoFragment 11-18 11:33:45.851: E/AndroidRuntime(8376): at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:285) 11-18 11:33:45.851: E/AndroidRuntime(8376): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:685) 11-18 11:33:45.851: E/AndroidRuntime(8376): ... 23 more
嵌套的Fragment布局如下所示（fragment_main.xml）
<ScrollView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:id="@+id/center_layout"
android:layout_width="match_parent"
android:layout_height="200dp"
android:orientation="horizontal" >
<fragment
android:id="@+id/hot_video_fragment"
android:layout_width="0dp"
android:layout_weight="2"
android:layout_height="match_parent"
class="com.tvie.ivideo.pad.main.HotVideoFragment" />
<fragment
android:id="@+id/my_channel_fragment"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="match_parent"
class="com.tvie.ivideo.pad.main.MyChannelFragment" />
</LinearLayout>
<fragment
android:id="@+id/recommand_fragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
class="com.tvie.ivideo.pad.main.RecommandFragment" />
</LinearLayout>
</ScrollView>Fragment嵌套和销毁问题
1、不要直接将Fragement写在XML文件里，这样会导致Fragment对象无法销毁，产生内存溢出。在代码动态的new 和add Fragement才是正确的做法。
2、使用抽屉方法，在XML文件里放两个LinearLayout，然后在代码中将Fragment加进这两个LinearLayout中。
要移动Fragment，就是移动LinearLayout，可以通过修改margin值来达到渐变移动的效果。
记得当Fragment移除屏幕的时候，detach掉它。
动态添加Fragment
参考1：初识Fragmentの动态添加
http://www.doc88.com/p-383778428274.html
参考2：Dynamically add fragment into fragment
http://stackoverflow.com/questions/7915413/dynamically-add-fragment-into-fragment
企图调用LinearLayout的addView方法添加Fragment（如下所示）
经过验证这个方法不可行
private void initializeFragments() {
Logger.v(TAG, "@initializeFragments.");
recmdFragment = new RecommandFragment();
hotFragment = new HotVideoFragment();
channelFragment = new MyChannelFragment();
linearLayout1.addView(recmdFragment.getView(),
new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
linearLayout2.addView(hotFragment.getView(),
new LayoutParams(linearLayout1.getMeasuredWidth() * 2 / 3, LayoutParams.MATCH_PARENT));
linearLayout2.addView(channelFragment.getView(),
new LayoutParams(linearLayout1.getMeasuredWidth() * 1 / 3, LayoutParams.MATCH_PARENT));
}参考stackoverflow网站上的资料，得到正确添加Fragment的方法
private void initializeFragments() {
Logger.v(TAG, "@initializeFragments.");
hotFragment = new HotVideoFragment();
channelFragment = new MyChannelFragment();
recmdFragment = new RecommandFragment();
FragmentTransaction trac = getFragmentManager().beginTransaction();
trac.add(R.id.hot_video_fragment, hotFragment);
trac.add(R.id.my_channel_fragment, channelFragment);
trac.add(R.id.recommand_fragment, recmdFragment);
trac.commit();
}再看下布局文件也被重新定义，将原来Fragment标记全部改为LinearLayout
<ScrollView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="300dp"
android:orientation="horizontal" >
<LinearLayout
android:id="@+id/hot_video_fragment"
android:layout_width="0dp"
android:layout_weight="2"
android:layout_height="match_parent"
android:orientation="vertical"/>
<LinearLayout
android:id="@+id/my_channel_fragment"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="match_parent"
android:orientation="vertical" />
</LinearLayout>
<LinearLayout
android:id="@+id/recommand_fragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" />
</LinearLayout>
</ScrollView>是在onCreateView方法调用initializeFragment的吗？NO，是在onLayoutChange方法中调用
private void initializeView() {
linearLayout1.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
@Override
public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight,
int oldBottom) {
initializeFragments();
linearLayout1.removeOnLayoutChangeListener(this);
}
});
}变量context竟然null值
先看打印出来的日志
11-18 13:44:49.531: V/MainFragment(21389): @onCreateView 11-18 13:44:49.541: V/MainFragment(21389): @initializeView. create each fragment. 11-18 13:44:49.541: V/MainFragment(21389): @onActivityCreated. data isn't null. data.size >> 5 11-18 13:44:49.541: V/HotVideoFragment(21389): @createHotImageView. context >> null
从日志来看：第二次启动推荐首页，先后要执行MainFragment的onCreateView方法，onActivityCreated方法，但是没有执行HotVideoFragment的onCreateView方法，onActivityCreated方法
新建Fragment会调用onCreate方法
嵌套在Fragment中的子Fragment。每次创建XXXFragment对象时，都会去调用onCreate方法。至少要等XXXFragment的onCreate等方法执行完（即创建完成）再去操作XXXFragment的界面元素才不出问题。
以下日志显示程序运行正常，没有出现context空指针问题
11-18 14:31:36.261: V/MainFragment(25136): @onCreateView 11-18 14:31:36.271: V/MainFragment(25136): @initializeView. create each fragment. 11-18 14:31:36.271: V/MainFragment(25136): @onActivityCreated. data isn't null. data.size >> 5 11-18 14:31:36.271: V/MainFragment(25136): @onActivityCreated. ready >> false 11-18 14:31:36.271: V/MainFragment(25136): @onLayoutChange 11-18 14:31:36.271: V/MainFragment(25136): @initializeFragments. add fragments to parent. 11-18 14:31:36.281: V/RecommandFragment(25136): @onCreate 11-18 14:31:36.281: V/RecommandFragment(25136): @onCreateView 11-18 14:31:36.291: V/HotVideoFragment(25136): @onCreate 11-18 14:31:36.291: V/HotVideoFragment(25136): @onCreateView 11-18 14:31:36.341: V/MainFragment(25136): @onActivityCreated. after 73 ms, ready >> true 11-18 14:31:36.351: V/MainFragment(25136): @renderInFragments
程序中的代码片段，在onActivityCreated方法中创建线程进入等待状态
final long start = System.currentTimeMillis();
new Thread() {
public void run() {
while(!isReady() || !recmdFragment.isReady() || !hotFragment.isReady()) {
try {
Thread.sleep(1);
} catch (InterruptedException e) { }
}
long end = System.currentTimeMillis();
Logger.v(TAG, "@onActivityCreated. after " + (end - start) + " ms, ready >> " + isReady());
handler.sendEmptyMessage(1);
}
}.start();其中新建XXXFragment的onCreate方法的调用执行只跟FragmentTransaction.add方法有关系。纯粹调用XXXFragment的构造方法不会去调用执行onCreate方法，可是执行FragmentTransaction.add方法之后就不同，XXXFragment的onCreate方法就被调用。同样，当调用FragmentTransaction.remove方法之后，XXXFragment的onDestroy方法也会被调用。当然，在调用FragmentTransaction的add或remove方法之后必须调用FragmentTransaction的commit方法。
先看下打印出来的日志
11-18 15:12:53.971: V/MainFragment(29470): @onCreateView 11-18 15:12:53.971: V/MainFragment(29470): @initializeView. create each fragment. 11-18 15:12:53.971: V/MainFragment(29470): @initializeFragments. add fragments by FragmentTransaction. 11-18 15:12:53.971: V/MainFragment(29470): @onActivityCreated. data isn't null. data.size >> 5 11-18 15:12:53.971: V/MainFragment(29470): @onActivityCreated. ready >> false 11-18 15:12:53.971: V/RecommandFragment(29470): @onCreate 11-18 15:12:53.971: V/RecommandFragment(29470): @onCreateView 11-18 15:12:53.981: V/HotVideoFragment(29470): @onCreate 11-18 15:12:53.981: V/HotVideoFragment(29470): @onCreateView 11-18 15:12:54.011: V/MainFragment(29470): @onActivityCreated. after 41 ms, ready >> false 11-18 15:12:54.011: V/MainFragment(29470): @onLayoutChange 11-18 15:12:54.021: V/MainFragment(29470): @renderInFragments ... 11-18 15:13:37.021: V/MainFragment(29470): @onDestroyView. remove fragments. by FragmentTransaction. 11-18 15:13:37.031: V/HotVideoFragment(29470): @onDestroyView 11-18 15:13:37.031: V/HotVideoFragment(29470): @onDestroy 11-18 15:13:37.031: V/RecommandFragment(29470): @onDestroyView 11-18 15:13:37.031: V/RecommandFragment(29470): @onDestroy
再看下调用FragmentTransaction的add和remove方法的代码片段
private void initializeFragments() {
Logger.v(TAG, "@initializeFragments. add fragments by FragmentTransaction.");
FragmentTransaction trac = getFragmentManager().beginTransaction();
trac.add(R.id.hot_video_fragment, hotFragment);
trac.add(R.id.my_channel_fragment, channelFragment);
trac.add(R.id.recommand_fragment, recmdFragment);
trac.commit();
}
@Override
public void onDestroyView() {
Logger.v(TAG, "@onDestroyView. remove fragments. by FragmentTransaction.");
super.onDestroyView();
FragmentTransaction trac = getFragmentManager().beginTransaction();
trac.remove(hotFragment);
trac.remove(channelFragment);
trac.remove(recmdFragment);
trac.commit();
hotFragment = null;
channelFragment = null;
recmdFragment = null;
linearLayout1 = null;
}
