我的Android进阶之旅------>Android之拖动条(SeekBar和RatingBar)的功能和用法-优快云博客

简介

下面通过一个使用拖动滑块改变图片透明度的实例来学习SeekBar和RatingBar

step1:新建一个项目MySeekBar

step2:编写应用的UI界面

a. /layout/seekbar.xml

<?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">
	<Button android:layout_width="fill_parent"
		android:layout_height="wrap_content" android:onClick="startRatingbar"
		android:text="start Ratingbar"/>
	<ImageView android:id="@+id/image" android:layout_width="fill_parent"
		android:layout_height="240px"
		android:src="@drawable/guitar" />
	
	<!-- 定义一个拖动条，并改变它的滑动外观 -->
	<SeekBar android:layout_width="fill_parent"
		android:layout_height="wrap_content" 
		android:max="255" 
		android:progress="255"
		android:id="@+id/seekbar"
		android:thumb="@drawable/star"
		/>
	
</LinearLayout>

b. /layout/ratingbar.xml

<?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">
	<Button android:layout_width="fill_parent"
		android:layout_height="wrap_content" android:onClick="startSeekBar"
		android:text="start SeekBar"/>
		
	<ImageView android:id="@+id/image" android:layout_width="fill_parent"
		android:layout_height="240px" android:src="@drawable/wall" />
	
	<!-- 定义一个星级评分条 -->
	<RatingBar android:id="@+id/ratingbar" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:max="255"
		android:progress="255" android:numStars="5" android:stepSize="0.5" />
		
	
</LinearLayout>

其中使用的图片有：

star.png

wall.jpg

guitar.jpg
step3:MySeekBar.java

package cn.roco.seekbar;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

public class MySeekBar extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.seekbar);
		final ImageView imageView=(ImageView) findViewById(R.id.image);
		SeekBar seekBar=(SeekBar) findViewById(R.id.seekbar);
		seekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
			
			@Override
			public void onStopTrackingTouch(SeekBar seekBar) {
			}
			
			@Override
			public void onStartTrackingTouch(SeekBar seekBar) {
			}
			
			//当拖动条的滑块位置发生改变时触发该方法
			@Override
			public void onProgressChanged(SeekBar seekBar, int progress,
					boolean fromUser) {
				//动态改变图片的透明度
				imageView.setAlpha(progress);
			}
		});
	}
	public void startRatingbar(View v){
		Intent intent=new Intent(MySeekBar.this,MyRatingBar.class);
		startActivity(intent);
	}
	
	
}

step4:MyRatingBar.java

package cn.roco.seekbar;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.RatingBar.OnRatingBarChangeListener;

public class MyRatingBar extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.ratingbar);
		final ImageView imageView=(ImageView) findViewById(R.id.image);
		RatingBar ratingBar=(RatingBar) findViewById(R.id.ratingbar);
		ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() {
			@Override
			public void onRatingChanged(RatingBar ratingBar, float rating,
					boolean fromUser) {
				imageView.setAlpha((int)(rating*255/5));
			}
		});
	}
	
	public void startSeekBar(View v){
		Intent intent=new Intent(MyRatingBar.this,MySeekBar.class);
		startActivity(intent);
	}
}

step5:AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="cn.roco.seekbar"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="8" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".MyRatingBar"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
 	<activity android:name=".MySeekBar"/>
    </application>
</manifest>

step6:部署应用到模拟器上，查看运行效果