ViewPager+Fragment使用中的Fragment生命周期

1.MainActivity代码如下

package com.example.administrator.viewpagerdemo;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.Window;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

private ViewPager viewPager;
private List<Fragment> fragments = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager) findViewById(R.id.viewPager);
FirstFragment firstF = new FirstFragment();
SecondFragment secondF = new SecondFragment();
ThirdFragment thirdF = new ThirdFragment();
fragments.add(firstF);
fragments.add(secondF);
fragments.add(thirdF);
viewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {
@Override
public android.support.v4.app.Fragment getItem(int i) {
return fragments.get(i);
}

@Override
public int getCount() {
return fragments.size();
}

});
}

}

2.FirstFragment代码如下

package com.example.administrator.viewpagerdemo;

import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
* Created by Administrator on 2016/5/5 0005.
*/
public class FirstFragment extends Fragment {

private final static String TAG = "FirstFragment";
//当fragment和activity关联的时候(Activity对象传递过来，即context)被调用
@Override
public void onAttach(Context context) {
Log.e(TAG,"onAttach");
super.onAttach(context);
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
Log.e(TAG,"onCreate");
super.onCreate(savedInstanceState);
}

@Nullable
@Override
//被调用用来创建与该fragment相关联的view控件结构
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.e(TAG,"onCreateView");
View view = inflater.inflate(R.layout.fragment, container, false);
TextView textView = (TextView) view.findViewById(R.id.textView);
textView.setText("first fragment");
return view;
}

@Override
//当activity的onCreate()方法返回时被调用
public void onActivityCreated() {
Log.e(TAG,"onActivityCreated");
super.onStart();
}

@Override
public void onStart() {
Log.e(TAG,"onStart");
super.onStart();
}

@Override
public void onResume() {
Log.e(TAG,"onResume");
super.onResume();
}

@Override
public void onPause() {
Log.e(TAG,"onPause");
super.onPause();
}

@Override
public void onStop() {
Log.e(TAG,"onStop");
super.onStop();
}

@Override
//当与fragment相关联的view控件结构被移除时调用
public void onDestroyView() {
Log.e(TAG,"onDestroyView");
super.onDestroyView();
}

@Override
public void onDestroy() {
Log.e(TAG,"onDestroy");
super.onDestroy();
}

@Override
//当fragment和activity失去关联时被调用
public void onDetach() {
Log.e(TAG,"onDetach");
super.onDetach();
}

}

SecondFragment和ThirdFragment代码同FirstFragment。

当页面显示时，ViewPager会自动初始化当前Fragment和当前Fragment左右两个Fragment。按照上面的代码，解释如下：当FirstFragment显示时，SecondFragment也进行了初始化，可以查看日志

05-05 11:25:30.606    1545-1545/? E/FirstFragment﹕ onAttach
05-05 11:25:30.606    1545-1545/? E/FirstFragment﹕ onCreate
05-05 11:25:30.606    1545-1545/? E/FirstFragment﹕ onCreateView
05-05 11:25:30.606    1545-1545/? E/FirstFragment﹕ onActivityCreated
05-05 11:25:30.622    1545-1545/? E/FirstFragment﹕ onStart
05-05 11:25:30.626    1545-1545/? E/FirstFragment﹕ onResume
05-05 11:25:30.630    1545-1545/? E/SecondFragment﹕ onAttach
05-05 11:25:30.630    1545-1545/? E/SecondFragment﹕ onCreate
05-05 11:25:30.630    1545-1545/? E/SecondFragment﹕ onCreateView
05-05 11:25:30.606    1545-1545/? E/FirstFragment﹕ onActivityCreated
05-05 11:25:30.674    1545-1545/? E/SecondFragment﹕ onStart
05-05 11:25:30.674    1545-1545/? E/SecondFragment﹕ onResume

当滑动到SecondFragment时，就会自动加载ThirdFragment，日志如下

05-05 11:26:12.270    1545-1545/? E/ThirdFragment﹕ onAttach
05-05 11:26:12.274    1545-1545/? E/ThirdFragment﹕ onCreate
05-05 11:26:12.274    1545-1545/? E/ThirdFragment﹕ onCreateView
05-05 11:26:12.274    1545-1545/? E/ThirdFragment﹕ onStart
05-05 11:26:12.274    1545-1545/? E/ThirdFragment﹕ onResume

注意：当切换到ThirdFragment时，FirstFragment会销毁View，日志如下：

05-05 11:27:53.590    1545-1545/? E/FirstFragment﹕ onPause
05-05 11:27:53.590    1545-1545/? E/FirstFragment﹕ onStop
05-05 11:27:53.594    1545-1545/? E/FirstFragment﹕ onDestroyView

然后当又切换到SecondFragment时，日志如下：

05-05 11:28:25.758    1545-1545/? E/FirstFragment﹕ onCreateView
05-05 11:28:25.762    1545-1545/? E/FirstFragment﹕ onStart
05-05 11:28:25.762    1545-1545/? E/FirstFragment﹕ onResume

又重新执行onCreateView，创建View。