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我创建了一个简单的Activity和Fragment生命周期调试应用程序,它通过报告对logcat的调用来简单地实现Activity lifecycle和Fragment lifecycle的每一个步骤.
以下是TestActivity和TestFragment类：
测试活动
public class TestActivity extends Activity { Context ct = null; @Override protected void onCreate(Bundle savedInstanceStatE) { super.onCreate(savedInstanceStatE); Log.e("ACT","onCreate called"); ct = getApplicationContext(); FrameLayout fl = new FrameLayout(ct); fl.setId(1000); TestFragment tf = new TestFragment(); getFragmentManager().begintransaction().add(fl.getId(),tf,"").commit(); setContentView(fl); } @Override protected void onStart() { Log.e("ACT","onStart called"); super.onStart(); } @Override protected void onResume() { Log.e("ACT","onResume called"); super.onResume(); } @Override protected void onPause() { Log.e("ACT","onPause called"); super.onPause(); } @Override protected void onStop() { Log.e("ACT","onStop called"); super.onStop(); } @Override protected void onDestroy() { Log.e("ACT","onDestroy called"); super.onDestroy(); } @Override protected void onRestart() { Log.e("ACT","onRestart called"); super.onRestart(); } }
TestFragment
public class TestFragment extends Fragment { Context ctFrag = null; @Override public void onAttach(Activity activity) { Log.e("FRAG","onAttach called"); super.onAttach(activity); } @Override public void onCreate(Bundle savedInstanceStatE) { super.onCreate(savedInstanceStatE); Log.e("FRAG","onCreate called"); } @Override public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceStatE) { Log.e("FRAG","onCreateView called"); ctFrag = ((TestActivity) getActivity()).ct; TextView tv = new TextView(ctFrag); tv.setText("My test TextView"); return tv; } @Override public void onActivityCreated(Bundle savedInstanceStatE) { Log.e("FRAG","onActivityCreated called"); super.onActivityCreated(savedInstanceStatE); } @Override public void onStart() { Log.e("FRAG","onStart called"); super.onStart(); } @Override public void onResume() { Log.e("FRAG","onResume called"); super.onResume(); } @Override public void onPause() { Log.e("FRAG","onPause called"); super.onPause(); } @Override public void onStop() { Log.e("FRAG","onStop called"); super.onStop(); } @Override public void onDestroyView() { Log.e("FRAG","onDestroyView called"); super.onDestroyView(); } @Override public void onDestroy() { Log.e("FRAG","onDestroy called"); super.onDestroy(); } @Override public void onDetach() { Log.e("FRAG","onDetach called"); super.onDetach(); } }
在初始化时,Logcat输出遵循预期顺序(启动活动,分片附加,生命周期调用发生等)：
01-29 10:12:50.270: E/ACT(3321): onCreate called 01-29 10:12:50.760: E/FRAG(3321): onAttach called 01-29 10:12:50.760: E/FRAG(3321): onCreate called 01-29 10:12:50.760: E/FRAG(3321): onCreateView called 01-29 10:12:50.770: E/FRAG(3321): onActivityCreated called 01-29 10:12:50.770: E/ACT(3321): onStart called 01-29 10:12:50.770: E/FRAG(3321): onStart called 01-29 10:12:50.770: E/ACT(3321): onResume called 01-29 10:12:50.770: E/FRAG(3321): onResume called
但问题是,当一个方向改变发生时,Android Documentation说：
这将表明它应该关闭活动及其内容,如生命周期建议(然后它)然后通过相同的有序过程重新创建活动在新的方向.这不会发生,似乎尝试重新创建片段,然后在活动娱乐中创建新的片段.
01-29 10:17:52.249: E/FRAG(3321): onPause called 01-29 10:17:52.259: E/ACT(3321): onPause called 01-29 10:17:52.269: E/FRAG(3321): onStop called 01-29 10:17:52.269: E/ACT(3321): onStop called 01-29 10:17:52.279: E/FRAG(3321): onDestroyView called 01-29 10:17:52.299: E/FRAG(3321): onDestroy called 01-29 10:17:52.299: E/FRAG(3321): onDetach called 01-29 10:17:52.299: E/ACT(3321): onDestroy called 01-29 10:17:52.650: E/FRAG(3321): onAttach called 01-29 10:17:52.650: E/FRAG(3321): onCreate called 01-29 10:17:52.650: E/ACT(3321): onCreate called 01-29 10:17:53.020: E/FRAG(3321): onCreateView called 01-29 10:17:53.020: E/FRAG(3321): onActivityCreated called 01-29 10:17:53.030: E/FRAG(3321): onAttach called 01-29 10:17:53.030: E/FRAG(3321): onCreate called 01-29 10:17:53.030: E/FRAG(3321): onCreateView called 01-29 10:17:53.030: E/FRAG(3321): onActivityCreated called 01-29 10:17:53.060: E/ACT(3321): onStart called 01-29 10:17:53.060: E/FRAG(3321): onStart called 01-29 10:17:53.060: E/FRAG(3321): onStart called 01-29 10:17:53.060: E/ACT(3321): onResume called 01-29 10:17:53.060: E/FRAG(3321): onResume called 01-29 10:17:53.060: E/FRAG(3321): onResume called
显然有很多解决方案可以解决这个问题,但是我的问题是为什么会发生这种情况？为什么一个片段引用被保留并重新创建,当它应该是该Activity的一部分,这被认为是完全被破坏和重新创建的？我可以通过故意将活动分开的碎片证明这一点.但是引发问题的原因是为什么在活动之前附加并重新创建了原始片段？它似乎并没有遵循Android进程的其余部分的逻辑生命周期.
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