Android中设计具有背景图的按钮—ImageButton的焦点及事件处理
ImageButtonDemo。
?第二步：编写Activity 的子类别：ImageButtonDemo，其程序代码如下：
?
package com.a3gs.imagebutton;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.TextView;
?
public class ImageButtonDemo extends Activity {
??? private TextView mTV;
??? private ImageButton imgBtn;
??? private Button btn;
???
??? @Override
??? public void onCreate(Bundle savedInstanceState) {
??????? super.onCreate(savedInstanceState);
??????? setContentView(R.layout.main);
???????
??????? mTV = (TextView) findViewById(R.id.tv);
??????? imgBtn= (ImageButton) findViewById(R.id.imgBtn);
??????? btn = (Button) findViewById(R.id.Btn);
???????
??????? // ImageButton的的onFous事件
??????? imgBtn.setOnFocusChangeListener(new ImageButton.OnFocusChangeListener(){
??????? ??? @Override
??????? ??? public void onFocusChange(View v, boolean hasFocus) {
??????? ?????? // TODO Auto-generated method stub
??????? ?????? if(hasFocus == true) {
??????? ?????????? imgBtn.setImageResource(R.drawable.full);
??????? ?????????? mTV.setText("图片按钮状态为:获得焦点");
??????? ?????? }else{
??????? ?????????? imgBtn.setImageResource(R.drawable.empty);
??????? ?????????? mTV.setText("图片按钮状态为:失去焦点");
??????? ?????? }
??????? ??? }
??????? });
???????
??????? // ImageButton的单击事件
??????? imgBtn.setOnClickListener(new ImageButton.OnClickListener(){
?????????? @Override
?????????? public void onClick(View v) {
????????????? // TODO Auto-generated method stub
????????????? imgBtn.setImageResource(R.drawable.full);
????????????? mTV.setText("图片按钮状态为:单击");
?????????? }
??????? });
???????
??????? // 普通按钮的单击事件
??????? btn.setOnClickListener(new Button.OnClickListener(){
?????????? @Override
?????????? public void onClick(View v) {
????????????? // TODO Auto-generated method stub
????????????? imgBtn.setImageResource(R.drawable.empty);
????????????? mTV.setText("您按的是普通按钮！");
?????????? }
??????? });
??? }
}
?
第三步：修改res/layout/main.xml，其代码如下：
?
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
??? android:orientation="vertical"
??? android:layout_width="fill_parent"
??? android:layout_height="fill_parent"
??? >
<TextView?
??? android:id="@+id/tv"
??? android:layout_width="fill_parent"
??? android:layout_height="wrap_content"
??? android:text="@string/hello"
??? />
<ImageButton
??? android:id="@+id/imgBtn"
??? android:layout_width="wrap_content"
??? android:layout_height="wrap_content"
??? android:src="@drawable/empty"
??? />
<Button
??? android:id="@+id/Btn"
??? android:layout_width="wrap_content"
??? android:layout_height="wrap_content"
??? android:text="Button按钮"
??? />
</LinearLayout>
?
扩展学习
?
除了在运行时用 onFocus() 与onClick() 事件来设置按钮背景图片外，Android 的MVC 设计理念，可以让程序运行之初就以xml 定义的方式来初始化ImageButton 的背景图，仅需先将图片导入res/drawable。
设置方法为在 res/drawable 下自行定义一个xml，主要针对按钮的state_focused、state_pressed 与drawable 属性作设置，如下所示：
drawable/imagebutton.xml
<?xml version="1.0" encoding="utf-8"?>
<selector
xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:state_focused="true"
android:state_pressed="false"
android:drawable="@drawable/btnfocused" />
<item
android:state_focused="true"
android:state_pressed="true"
android:drawable="@drawable/btnfocusedpressed" />
<item
android:state_focused="false"
android:state_pressed="true"
android:drawable="@drawable/btnpressed" />
<item android:drawable="@drawable/btndefault" />
</selector>
然后，在main.xml 中将advancedbutton 赋值给Button 组件中background 的属性。
layout/main.xml
<Button
android:id="@+id/myButton1"
android:background="@drawable/ imagebutton "
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/str_button1"
/>
