Android ViewStub控件使用
ViewStub是android中view的一种优化方案，它的目的是在不需要显示view的时候不去加载view，这样在view的创建时期，减少了加载的资源，优化了view。
下面就用代码来说明如何使用viewstub。
先上图
功能很简单，当点击traggle时，下面的viewstub会加载其中预置的layout，再次点击时，隐藏viewstub。
代码如下
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button android:id="@+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Traggle" />
<ViewStub android:id="@+id/stub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout="@layout/<span style="font-family: Arial, Helvetica, sans-serif;">text_layout</span>" />
<Button android:id="@+id/btn1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Traggle2" />
</LinearLayout>
text_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="ddddddddddddddddddddddddd \n
ddddddddddddddddddddddddddddddddddddddd \n
ddddddddddddddddddddddddddddddddddddddd \n
ddddddddddddddddddddddddddddddddddddddd \n
ddddddddddddddddddddddddddddddddddddddd \n
ddddddddddddddddddddddddddddddddddddddd \n
ddddddddddddddddddddddddddddddddddddd" >
</TextView>
Main_Activity.java
package com.example.listscroll;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Context;
import android.os.Bundle;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.ViewStub;
import android.view.WindowManager;
import android.view.animation.AnimationUtils;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends Activity {
private boolean mShowed;
private View mTextPanel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (mTextPanel == null) {
mTextPanel = ((ViewStub) findViewById(R.id.stub)).inflate();
}
if (mShowed == false) {
mShowed = true;
showPanel(mTextPanel, true);
} else {
mShowed = false;
hidePanel(mTextPanel, true);
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
private void showPanel(View panel, boolean slideUp) {
panel.startAnimation(AnimationUtils.loadAnimation(this,
slideUp ? R.anim.slide_in : R.anim.slide_out_top));
panel.setVisibility(View.VISIBLE);
}
private void hidePanel(View panel, boolean slideDown) {
panel.startAnimation(AnimationUtils.loadAnimation(this,
slideDown ? R.anim.slide_out : R.anim.slide_in_top));
panel.setVisibility(View.GONE);
}
}
下面是4个简单的动画效果，展示viewstub的加载
slide_in_top.xml<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<translate
android:duration="200"
android:fromYDelta="0%"
android:toYDelta="-100%" />
<alpha
android:duration="200"
android:fromAlpha="1.0"
android:toAlpha="0.0" />
</set>
slide_in.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<translate
android:duration="200"
android:fromYDelta="100%"
android:toYDelta="0%" />
<alpha
android:duration="200"
android:fromAlpha="0.0"
android:toAlpha="1.0" />
</set>
slide_out_top.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<translate
android:duration="200"
android:fromYDelta="-100%"
android:toYDelta="0%" />
<alpha
android:duration="200"
android:fromAlpha="0.0"
android:toAlpha="1.0" />
</set>
slide_out.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<translate
android:duration="200"
android:fromYDelta="0%"
android:toYDelta="100%" />
<alpha
android:duration="200"
android:fromAlpha="1.0"
android:toAlpha="0.0" />
</set>
ViewStub中加载layout的代码是
public View inflate() {
final ViewParent viewParent = getParent();// 获取当前view的父view，用于获取需要加载的layout的index
if (viewParent != null && viewParent instanceof ViewGroup) {
if (mLayoutResource != 0) {
final ViewGroup parent = (ViewGroup) viewParent;
final LayoutInflater factory;
if (mInflater != null) {
factory = mInflater;
} else {
factory = LayoutInflater.from(mContext);
}
final View view = factory.<strong><span style="font-size:14px;color:#ff0000;">inflate</span></strong>(mLayoutResource, parent, false);// 获取需要加载的layout
if (mInflatedId != NO_ID) {
view.setId(mInflatedId);
}
final int index = parent.indexOfChild(this);
parent.removeViewInLayout(this);// 删除之前加载的view
final ViewGroup.LayoutParams layoutParams = getLayoutParams();
if (layoutParams != null) {
parent.addView(view, index, layoutParams);
} else {
parent.<strong><span style="font-size:14px;color:#ff0000;">addView</span></strong>(view, index);// 添加view
}
mInflatedViewRef = new WeakReference<View>(view);
if (mInflateListener != null) {
mInflateListener.onInflate(this, view);
}
return view;
} else {
throw new IllegalArgumentException("ViewStub must have a valid layoutResource");
}
} else {
throw new IllegalStateException("ViewStub must have a non-null ViewGroup viewParent");
}
}