[英]Correctly implementing PagerAdapter in Android
I have problems with implementation of my custom PagerAdapter and using it with a ViewPager.我在实现我的自定义 PagerAdapter 并将其与 ViewPager 一起使用时遇到问题。 This sample PagerAdapter has 10 items, every item is a button with it's index as text.
此示例 PagerAdapter 有 10 个项目,每个项目都是一个按钮,其索引为文本。 When I run my program, I see a button with text '1' insted of '0'.
当我运行我的程序时,我看到一个按钮,其文本为“1”而不是“0”。 And when I swipe to other items I get only blank views.
当我滑动到其他项目时,我只会看到空白视图。 When I swipe backwards sometimes I see a button with some number, but it disappears (maybe it is destroying and I remove it from the container), and sometimes I see a button with a number, but the number changes after the swipe (I think I create a new Button and I add it to the container, and for some reasons the viewpager shows this new button).
当我向后滑动时,有时我会看到一个带有一些数字的按钮,但它消失了(也许它正在破坏,我将其从容器中移除),有时我会看到一个带有数字的按钮,但滑动后数字会发生变化(我认为我创建了一个新的 Button 并将其添加到容器中,出于某些原因,viewpager 显示了这个新按钮)。
How can I fix this implementation?我该如何修复这个实现? I haven't seen difference in examples.
我没有看到示例的差异。
My PagerAdapter implementation:我的 PagerAdapter 实现:
public class MyPagerAdapter extends PagerAdapter {
@Override
public int getCount() {
return 10;
}
@Override
public boolean isViewFromObject(View view, Object o) {
return o.getClass()==view.getClass();
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
Button button = new Button(container.getContext());
ViewGroup.LayoutParams params = new ActionBar.LayoutParams(-1,-1);
button.setLayoutParams(params);
button.setText(String.valueOf(position));
container.addView(button);
return button;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((Button)object);
}
}
And my Activity:我的活动:
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ViewPager pager = (ViewPager) findViewById(R.id.pager);
pager.setAdapter(new MyPagerAdapter());
}
}
Here is complete code: 这是完整的代码:
xml layout: xml布局:
<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.example.androidviewpagerapp.MainActivity" >
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
MyPagerAdapter class: MyPagerAdapter类:
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;
public class MyPagerAdapter extends PagerAdapter {
@Override
public int getCount() {
return 10;
}
@Override
public boolean isViewFromObject(View view, Object o) {
return o==view;
}
@Override
public Object instantiateItem(final ViewGroup container, int position) {
Button button = new Button(container.getContext());
ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
button.setLayoutParams(params);
button.setText(String.valueOf(position));
final int page = position;
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(container.getContext(), "You clicked: " + page + ". page.", Toast.LENGTH_SHORT).show();
}
});
container.addView(button);
return button;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((Button)object);
}
}
MainActivity: 主要活动:
import android.support.v4.view.ViewPager;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
ViewPager viewPager;
MyPagerAdapter myPagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager)findViewById(R.id.pager);
myPagerAdapter = new MyPagerAdapter();
viewPager.setAdapter(myPagerAdapter);
}
}
You will see that Buttons are full screen. 你会看到按钮是全屏的。 To avoid that you need to create some layout (like LinearLayout) and add button to that layout.
为了避免这种情况,您需要创建一些布局(如LinearLayout)并向该布局添加按钮。
Example: 例:
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;
public class MyPagerAdapter extends PagerAdapter {
@Override
public int getCount() {
return 10;
}
@Override
public boolean isViewFromObject(View view, Object o) {
return o==view;
}
@Override
public Object instantiateItem(final ViewGroup container, int position) {
Button button = new Button(container.getContext());
ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
button.setLayoutParams(params);
button.setText(String.valueOf(position));
LinearLayout layout = new LinearLayout(container.getContext());
layout.setOrientation(LinearLayout.VERTICAL);
ViewGroup.LayoutParams layoutParams = new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
//add buton to layout
layout.addView(button);
final int page = position;
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(container.getContext(), "You clicked: " + page + ". page.", Toast.LENGTH_SHORT).show();
}
});
//to container add layout instead of button
container.addView(layout);
//return layout instead of button
return layout;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
//cast to LinearLayout
container.removeView((LinearLayout)object);
}
}
if you want to inflate views in pager you must have to implement two methods.
如果要在寻呼机中扩充视图,则必须实现两种方法。 instantiateItem and destroyItem
instantiateItem和destroyItem
public class DialogPagerAdapter extends PagerAdapter {
private Context mContext;
//view inflating..
@Override
public Object instantiateItem(ViewGroup collection, int position) {
LayoutInflater inflater = LayoutInflater.from(mContext);
ViewGroup layout = (ViewGroup) inflater.inflate(R.layout.account_dialog_signin_viewpagers,
collection, false);
TextView tvLabel = (TextView) layout.findViewById(R.id.textView);
switch (position) {
case 0:
tvLabel.setText("Log In");
tvLabel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
}
});
break;
case 1:
tvLabel.setText("Sign Up");
tvLabel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
}
});
break;
case 2:
tvLabel.setText("Send Reset Link");
tvLabel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//onOptionClickForgot.OnOptionClick();
}
});
break;
}
collection.addView(layout);
return layout;
}
@Override
public void destroyItem(ViewGroup collection, int position, Object view) {
collection.removeView((View) view);
}
@Override
public int getCount() {
return 3;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
Simply call it like 简单地称之为
viewPager.setAdapter(new DialogPagerAdapter);
xml XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="@dimen/dialog_button_height"
android:paddingLeft="@dimen/dimen_2"
android:paddingRight="@dimen/dimen_2"
android:minHeight="@dimen/dialog_button_height">
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerInParent="true"
android:gravity="center"
android:text="@string/app_name"
android:textColor="@color/white"
android:textSize="@dimen/text_size_medium" />
</RelativeLayout>
Here i post ViewPagerAdapter
that attached between TabLayout
to ViewPager
在这里,我发布了附加在
TabLayout
和ViewPagerAdapter
之间的ViewPager
public class ViewPagerAdapter extends FragmentPagerAdapter {
ArrayList<String> titleList = new ArrayList<>();
List<Fragment> fragment = new ArrayList<>();
public void addFragment(String title, Fragment fragment) {
this.titleList.add(title);
this.fragment.add(fragment);
}
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
@NonNull
@Override
public Fragment getItem(int position) {
return fragment.get(position);
}
@Override
public int getCount() {
return titleList.size();
}
public CharSequence getPageTitle(int position) {
return titleList.get(position);
}
}
How to use ViewPagerAdapter
.如何使用
ViewPagerAdapter
。
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment("TAB 1", new YOUR_FRAGMENT1());
adapter.addFragment("TAB 2", new YOUR_FRAGMENT2());
// Keep adding fragments.
viewPager.setAdapter(adapter);
tabLayout.setupWithViewPager(viewPager);
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