Android 基础知识详解

1:Activity与Fragment的生命周期。

Activity的生命周期:

1) onCreate():当Activity第一次被创建时调用，完成活动的初始化操作.
2) onStart(): 当用户可以看到这个Activity时调用
3)onResume(): 当获得了用户的焦点时，就是用户点击屏幕
4)onPause():当系统准备启动或回复另一个活动时调用.在这个方法中将一些小号CPU的资源释放，保存一些重要数据。
5)onStop():当活动完全不可见时调用,当新启动的活动时，像对话框式的，还处于可见时，该方法是不会调用.
6)onDestroy():活动被销毁时调用
7)onRestart():当活动有停止状态变为运行状态时调用.

Fragment的生命周期:

对比图:

测试代码：

 import android.app.Activity;  
 import android.app.ListFragment;  
 import android.os.Bundle;  
 import android.util.Log;  
 import android.view.LayoutInflater;  
 import android.view.View;  
 import android.view.ViewGroup;  
 import android.widget.ArrayAdapter;  
 import android.widget.ListView;  

  /** 
        * Demonstration of using ListFragment to show a list of items 
        * from a canned array. 
       */  

 public class FragmentListArray extends Activity {  

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    Log.e("HJJ", "Activity &&&& onCreate...");  
    // Create the list fragment and add it as our sole content.  
    if (getFragmentManager().findFragmentById(android.R.id.content) == null) {  
        ArrayListFragment list = new ArrayListFragment();  
        getFragmentManager().beginTransaction().add(android.R.id.content, list).commit();  
    }  
}  

@Override  
protected void onStart() {  
    // TODO Auto-generated method stub  
    super.onStart();  
    Log.e("HJJ", "Activity &&&& onStart...");  
}  

@Override  
protected void onResume() {  
    // TODO Auto-generated method stub  
    super.onResume();  
    Log.e("HJJ", "Activity &&&& onResume...");  
}  

@Override  
protected void onStop() {  
    // TODO Auto-generated method stub  
    super.onStop();  
    Log.e("HJJ", "Activity &&&& onStop...");  
}  

@Override  
protected void onPause() {  
    // TODO Auto-generated method stub  
    super.onPause();  
    Log.e("HJJ", "Activity &&&& onPause...");  
}  

@Override  
protected void onDestroy() {  
    // TODO Auto-generated method stub  
    super.onDestroy();  
    Log.e("HJJ", "Activity &&&& onDestroy...");  
}  

public static class ArrayListFragment extends ListFragment {  

    @Override  
    public void onAttach(Activity activity) {  
        // TODO Auto-generated method stub  
        Log.e("HJJ", "ArrayListFragment **** onAttach...");  
        super.onAttach(activity);  
    }  

    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        // TODO Auto-generated method stub  
        Log.e("HJJ", "ArrayListFragment **** onCreate...");  
        super.onCreate(savedInstanceState);  
    }  

    @Override  
    public View onCreateView(LayoutInflater inflater, ViewGroup container,  
            Bundle savedInstanceState) {  
        // TODO Auto-generated method stub  
        Log.e("HJJ", "ArrayListFragment **** onCreateView...");  
        return super.onCreateView(inflater, container, savedInstanceState);  
    }  

    @Override  
    public void onActivityCreated(Bundle savedInstanceState) {  
        super.onActivityCreated(savedInstanceState);  
        Log.e("HJJ", "ArrayListFragment **** onActivityCreated...");  
        String[] array = new String[]{"C++", "JAVA", "PYTHON"};  
        setListAdapter(new ArrayAdapter(getActivity(),  
                android.R.layout.simple_list_item_1, array));  
    }  

    @Override  
    public void onStart() {  
        // TODO Auto-generated method stub  
        Log.e("HJJ", "ArrayListFragment **** onStart...");  
        super.onStart();  
    }  

    @Override  
    public void onResume() {  
        Log.e("HJJ", "ArrayListFragment **** onResume...");  
        // TODO Auto-generated method stub  
        super.onResume();  
    }  

    @Override  
    public void onPause() {  
        Log.e("HJJ", "ArrayListFragment **** onPause...");  
        // TODO Auto-generated method stub  
        super.onPause();  
    }  

    @Override  
    public void onStop() {  
        Log.e("HJJ", "ArrayListFragment **** onStop...");  
        // TODO Auto-generated method stub  
        super.onStop();  
    }  

    @Override  
    public void onDestroyView() {  
        Log.e("HJJ", "ArrayListFragment **** onDestroyView...");  
        // TODO Auto-generated method stub  
        super.onDestroyView();  
    }  

    @Override  
    public void onDestroy() {  
        // TODO Auto-generated method stub  
        Log.e("HJJ", "ArrayListFragment **** onDestroy...");  
        super.onDestroy();  
    }  

    @Override  
    public void onDetach() {  
        Log.e("HJJ", "ArrayListFragment **** onDetach...");  
        // TODO Auto-generated method stub  
        super.onDetach();  
    }  

    @Override  
    public void onListItemClick(ListView l, View v, int position, long id) {  
        Log.i("FragmentList", "Item clicked: " + id);  
    }  
}  

测试结果:

onCreate过程  
01-22 15:30:28.091: E/HJJ(10315): Activity &&&& onCreate...  
01-22 15:30:28.091: E/HJJ(10315): ArrayListFragment **** onAttach...  
01-22 15:30:28.091: E/HJJ(10315): ArrayListFragment **** onCreate...  
01-22 15:30:28.115: E/HJJ(10315): ArrayListFragment **** onCreateView...  
01-22 15:30:28.123: E/HJJ(10315): ArrayListFragment **** onActivityCreated...  

onStart过程  
01-22 15:30:28.123: E/HJJ(10315): Activity &&&& onStart...  
01-22 15:30:28.123: E/HJJ(10315): ArrayListFragment **** onStart...  

onResume过程  
01-22 15:30:28.123: E/HJJ(10315): Activity &&&& onResume...  
01-22 15:30:28.123: E/HJJ(10315): ArrayListFragment **** onResume...  

onPause过程  
01-22 15:31:26.748: E/HJJ(10315): ArrayListFragment **** onPause...  
01-22 15:31:26.748: E/HJJ(10315): Activity &&&& onPause...  

onStop过程  
01-22 15:31:27.638: E/HJJ(10315): ArrayListFragment **** onStop...  
01-22 15:31:27.638: E/HJJ(10315): Activity &&&& onStop...  

onStart过程  
01-22 15:31:57.537: E/HJJ(10315): Activity &&&& onStart...  
01-22 15:31:57.537: E/HJJ(10315): ArrayListFragment **** onStart...  

onResume过程  
01-22 15:31:57.537: E/HJJ(10315): Activity &&&& onResume...  
01-22 15:31:57.537: E/HJJ(10315): ArrayListFragment **** onResume...  

onPause过程  
01-22 15:32:47.412: E/HJJ(10315): ArrayListFragment **** onPause...  
01-22 15:32:47.412: E/HJJ(10315): Activity &&&& onPause...  

onStop过程  
01-22 15:32:47.865: E/HJJ(10315): ArrayListFragment **** onStop...  
01-22 15:32:47.865: E/HJJ(10315): Activity &&&& onStop...  

onDestroy过程  
01-22 15:32:47.865: E/HJJ(10315): ArrayListFragment **** onDestroyView...  
01-22 15:32:47.865: E/HJJ(10315): ArrayListFragment **** onDestroy...  
01-22 15:32:47.865: E/HJJ(10315): ArrayListFragment **** onDetach...  
01-22 15:32:47.865: E/HJJ(10315): Activity &&&& onDestroy...