一、Demo所涉及的部分代码
1.MainActivity的布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:background="#ffffff"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="@+id/main_frame_layout"
android:background="#dddddd"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="0dp">
</FrameLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="48dp">
<Button
android:id="@+id/btn1"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent"
android:background="#ffffff"
android:text="首页"/>
<Button
android:id="@+id/btn2"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent"
android:background="#ffffff"
android:text="消息"/>
</LinearLayout>
</LinearLayout>
MainActivity的代码:
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "MainActivity";
private FrameLayout main_frame_layout;
private Button btn1;
private Button btn2;
private Button btn3;
FragmentA f1;
FragmentB f2;
FragmentC f3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
main_frame_layout = findViewById(R.id.main_frame_layout);
btn1 = findViewById(R.id.btn1);
btn2 = findViewById(R.id.btn2);
btn3 = findViewById(R.id.btn3);
btn1.setOnClickListener(this);
btn2.setOnClickListener(this);
btn3.setOnClickListener(this);
initFragment1();
Log.i(TAG, "onCreate()");
}
@Override
protected void onStart() {
super.onStart();
Log.i(TAG, "onStart()");
}
@Override
protected void onResume() {
super.onResume();
Log.i(TAG, "onResume()");
}
@Override
protected void onPause() {
super.onPause();
Log.i(TAG, "onPause()");
}
@Override
protected void onStop() {
super.onStop();
Log.i(TAG, "onStop()");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.i(TAG, "onDestroy()");
}
private void initFragment1() {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
//第一种方式使用add
if (f1 == null) {
f1 = new FragmentA("首页");
transaction.add(R.id.main_frame_layout, f1);
}
//隐藏
hideFragment(transaction);
//展示
transaction.show(f1);
// //第二种方式 replace
// if(f1==null){
// f1=new FragmentA("首页");
// }
// transaction.replace(R.id.main_frame_layout,f1);
// transaction.commit();
}
private void hideFragment(FragmentTransaction transaction) {
if (f1 != null) {
transaction.hide(f1);
}
if (f2 != null) {
transaction.hide(f2);
}
if (f3 != null) {
transaction.hide(f3);
}
}
public void initFragment2() {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
//第一种方式使用add
if (f2 == null) {
f2 = new FragmentB("消息");
transaction.add(R.id.main_frame_layout, f2);
}
//隐藏
hideFragment(transaction);
//展示
transaction.show(f2);
// //第二种方式 replace
// if (f2 == null) {
// f2 = new FragmentB("消息");
// }
// transaction.replace(R.id.main_frame_layout, f2);
//
// transaction.commit();
}
@Override
public void onClick(View view) {
if (view == btn1) {
initFragment1();
} else if (view == btn2) {
initFragment2();
} else if (view == btn3) {
initFragment3();
}
}
private void initFragment3() {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
//第一种方式使用add
if (f3 == null) {
f3 = new FragmentC("消息");
transaction.add(R.id.main_frame_layout, f3);
}
//隐藏
hideFragment(transaction);
//展示
transaction.show(f3);
// //第二种方式 replace
// if (f3 == null) {
// f3 = new FragmentC("消息");
// }
// transaction.replace(R.id.main_frame_layout, f3);
//transaction.commit();
}
}
FragmentA:
public class FragmentA extends Fragment {
private static final String TAG="FragmentA";
private TextView tv;
private String name;
public FragmentA(String fName){
this.name = fName;
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.i(TAG,"onAttach()");
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i(TAG,"onCreate()");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_,container,false);
tv = (TextView) view.findViewById(R.id.fragment_tv);
tv.setText(name);
tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
tv.setText("我变了-" + name);
}
});
Log.i(TAG,"onCreatedView()");
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.i(TAG,"onActivityCreated()");
}
@Override
public void onPause() {
super.onPause();
Log.i(TAG,"onPause()");
}
@Override
public void onStop() {
super.onStop();
Log.i(TAG,"onStop()");
}
@Override
public void onDestroyView() {
super.onDestroyView();
Log.i(TAG,"onDestroyView()");
}
@Override
public void onDetach() {
super.onDetach();
Log.i(TAG,"onDettach()");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.i(TAG,"onDestroy()");
}
}
FragmentA对应的布局文件:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#dddddd">
<TextView
android:id="@+id/fragment_tv"
android:layout_centerInParent="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="fragment"
android:textColor="#000000"/>
</RelativeLayout>
FragmnetB、FragmentC与FragmentA的代码是一样的
二、使用add、hide、show的方式添加Fragment
1、程序一运行,首先加载的FragmentA对应的界面此时所涉及的生命周期方法是:
MainActivity: onCreate()
FragmentA: onAttach()
FragmentA: onCreate()
FragmentA: onCreatedView()
FragmentA: onActivityCreated()
MainActivity: onStart()
MainActivity: onResume()
2、此时切换到FragmnetB所涉及的生命周期方法有:
FragmentB: onAttach()
FragmentB: onCreate()
FragmentB: onCreatedView()
FragmentB: onActivityCreated()
3、在切换回FraagmentA
2019-08-02 20:04:16.874 25640-25640/com.example.testfragment I/ViewRootImpl: jank_removeInvalidNode all the node in jank list is out of time
4、然后在点击Home键后执行的生命周期方法
FragmentA: onPause()
FragmentB: onPause()
MainActivity: onPause()
FragmentA: onStop()
FragmentB: onStop()
MainActivity: onStop()
5、点击桌面应用图标在进去当前应用:
MainActivity: onStart()
MainActivity: onResume()
6、点击返回键退出应用
FragmentA: onPause()
FragmentB: onPause()
MainActivity: onPause()
FragmentA: onStop()
FragmentB: onStop()
MainActivity: onStop()
FragmentA: onDestroyView()
FragmentA: onDestroy()
FragmentA: onDettach()
FragmentB: onDestroyView()
FragmentB: onDestroy()
FragmentB: onDettach()
MainActivity: onDestroy()
三、使用replace方式替换
1、第一次启动程序
MainActivity: onCreate()
FragmentA: onAttach()
FragmentA: onCreate()
FragmentA: onCreatedView()
FragmentA: onActivityCreated()
MainActivity: onStart()
MainActivity: onResume()
2、切换至FragmentB
FragmentB: onAttach()
FragmentB: onCreate()
FragmentA: onPause()
FragmentA: onStop()
FragmentA: onDestroyView()
FragmentA: onDestroy()
FragmentA: onDettach()
FragmentB: onCreatedView()
FragmentB: onActivityCreated()
3、切换至FragmentC
FragmentC: onAttach()
FragmentC: onCreate()
FragmentB: onPause()
FragmentB: onStop()
FragmentB: onDestroyView()
FragmentB: onDestroy()
FragmentB: onDettach()
FragmentC: onCreatedView()
FragmentC: onActivityCreated()
4、此时按Home键
FragmentC: onPause()
MainActivity: onPause()
FragmentC: onStop()
MainActivity: onStop()
5、在按图标重新启动应用程序
MainActivity: onStart()
MainActivity: onResume()
6、此时在按返回键
FragmentA: onPause()
MainActivity: onPause()
FragmentA: onStop()
MainActivity: onStop()
FragmentA: onDestroyView()
FragmentA: onDestroy()
FragmentA: onDettach()
MainActivity: onDestroy()
四、add方式和replace方式的区别
add、hide、show方式添加Fragmnet,再次切换回来时不会重新创建该Fragment的实例~ 直接复用
replace方式添加的Fragment,再次切换回来时会重新创建Fragment的实例,每切换一次创建一次~
五、点击Home键返回桌面,在想让应用重新启动的方式有?
①点击应用图标
②多任务中点击启动
③也有可能是,系统内存不足了,此时应用被杀死了,在被重新启动