一手遮天 Android - view（集合类）: ViewPager 和 FragmentPagerAdapter
一手遮天 Android - view（集合类）: ViewPager 和 FragmentPagerAdapter
示例如下:
/view/collection/ViewPagerDemo3.java
/**
* ViewPager - 页面切换控件
* setCurrentItem() - 指定 ViewPager 当前显示的页面的索引位置
* setAdapter() - 指定用于为 ViewPager 呈现数据的 PagerAdapter 对象
*
* 本例演示
* 1、如何通过自定义的 FragmentPagerAdapter 来为 ViewPager 对象提供数据
* 2、FragmentPagerAdapter 会缓存 3 个页，即当前页、左边页和右边页
* 未被缓存的 fragment 不会调用其 destroy
* 3、FragmentStatePagerAdapter 会缓存 3 个页，即当前页、左边页和右边页
* 未被缓存的 fragment 会调用其 destroy
*/
package com.webabcd.androiddemo.view.collection;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;
import androidx.viewpager.widget.ViewPager;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ViewGroup;
import com.webabcd.androiddemo.R;
import java.util.ArrayList;
import java.util.List;
public class ViewPagerDemo3 extends AppCompatActivity {
private ViewPager mViewPager1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_collection_viewpagerdemo3);
mViewPager1 = findViewById(R.id.viewPager1);
sample();
}
private void sample() {
// 用于保存 ViewPager 的每个 fragment
final ArrayList fragmentList = new ArrayList<Fragment>();
fragmentList.add(ViewPagerDemo3_Fragment.newInstance(0xffff0000));
fragmentList.add(ViewPagerDemo3_Fragment.newInstance(0xff00ff00));
fragmentList.add(ViewPagerDemo3_Fragment.newInstance(0xff0000ff));
fragmentList.add(ViewPagerDemo3_Fragment.newInstance(0xff000000));
fragmentList.add(ViewPagerDemo3_Fragment.newInstance(0xffffffff));
// 实例化自定义的 FragmentPagerAdapter
MyFragmentPagerAdapter myFragmentPagerAdapter = new MyFragmentPagerAdapter(getSupportFragmentManager(), fragmentList);
// 指定 ViewPager 的 FragmentPagerAdapter
mViewPager1.setAdapter(myFragmentPagerAdapter);
}
/**
* 自定义 FragmentPagerAdapter 用于为 ViewPager 提供数据
*/
class MyFragmentPagerAdapter extends FragmentPagerAdapter {
private List<Fragment> mFragmentList;
private FragmentManager mFragmentManager;
public MyFragmentPagerAdapter(FragmentManager fragmentManager, List<Fragment> fragmentList){
super(fragmentManager);
this.mFragmentManager = fragmentManager;
this.mFragmentList = fragmentList;
}
@Override
public int getCount() {
return mFragmentList.size();
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
return super.instantiateItem(container, position);
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
}
}
\view\collection\ViewPagerDemo3_Fragment.java
/**
* 引用示例参见 view/collection/ViewPagerDemo3.java
*/
package com.webabcd.androiddemo.view.collection;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.webabcd.androiddemo.R;
import com.webabcd.androiddemo.utils.Helper;
public class ViewPagerDemo3_Fragment extends Fragment {
private final String LOG_TAG = "VP_Fragment";
private int mBackgroundColor;
public static ViewPagerDemo3_Fragment newInstance(int backgroundColor) {
ViewPagerDemo3_Fragment fragment = new ViewPagerDemo3_Fragment();
Bundle args = new Bundle();
args.putInt("backgroundColor", backgroundColor);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mBackgroundColor = getArguments().getInt("backgroundColor");
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_view_collection_viewpagerdemo3, container, false);
view.setBackgroundColor(mBackgroundColor);
// 用于验证 FragmentPagerAdapter 会缓存 3 个页，即当前页、左边页和右边页；未被缓存的 fragment 不会调用其 destroy
Log.d(LOG_TAG + "_" + Helper.int2Hex(mBackgroundColor), "onCreateView");
return view;
}
@Override
public void onResume() {
// 用于验证 FragmentPagerAdapter 会缓存 3 个页，即当前页、左边页和右边页；未被缓存的 fragment 不会调用其 destroy
Log.d(LOG_TAG + "_" + Helper.int2Hex(mBackgroundColor), "onResume");
super.onResume();
}
@Override
public void onPause() {
// 用于验证 FragmentPagerAdapter 会缓存 3 个页，即当前页、左边页和右边页；未被缓存的 fragment 不会调用其 destroy
Log.d(LOG_TAG + "_" + Helper.int2Hex(mBackgroundColor), "onPause");
super.onPause();
}
@Override
public void onDestroy() {
// 用于验证 FragmentPagerAdapter 会缓存 3 个页，即当前页、左边页和右边页；未被缓存的 fragment 不会调用其 destroy
Log.d(LOG_TAG + "_" + Helper.int2Hex(mBackgroundColor), "onDestroy");
super.onDestroy();
}
}
/layout/activity_view_collection_viewpagerdemo3.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.viewpager.widget.ViewPager
android:id="@+id/viewPager1"
android:layout_width="match_parent"
android:layout_height="match_parent">
</androidx.viewpager.widget.ViewPager>
</LinearLayout>
/layout/fragment_view_collection_viewpagerdemo3.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
