Android 通过seekBar设置图片透明度

Java代码：

package com.example.android07_widget;import android.content.Intent;import android.os.Bundle;import android.support.annotation.Nullable;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.ImageView;import android.widget.SeekBar;/** * Created by Administrator on 2017/7/19 0019. */public class MainActivitythird extends AppCompatActivity {    private ImageView iv_mainthird_image;    private int  currentAlpta=255;    private SeekBar sb_mainthird_seekBar;    private int n=R.drawable.s10;    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_mainthird);        iv_mainthird_image = (ImageView) findViewById(R.id.iv_mainthird_image);        sb_mainthird_seekBar = (SeekBar) findViewById(R.id.sb_mainthird_seekBar);        //设置默认清晰度        iv_mainthird_image.setImageAlpha(currentAlpta);        //设置一张默认默认图片        iv_mainthird_image.setImageResource(n);        //设置最大进度值        sb_mainthird_seekBar.setMax(255);        //进度条停止的最大值        sb_mainthird_seekBar.setProgress(255);        //通过SeekBar进度条，修改图片透明度        sb_mainthird_seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {            @Override            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {                currentAlpta=i;                iv_mainthird_image.setImageAlpha(currentAlpta);            }            @Override            public void onStartTrackingTouch(SeekBar seekBar) {            }            @Override            public void onStopTrackingTouch(SeekBar seekBar) {            }        });    }}

xml代码： 

<?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">    <SeekBar        android:id="@+id/sb_mainthird_seekBar"        android:layout_width="match_parent"        android:layout_height="wrap_content" />  <ImageView      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:id="@+id/iv_mainthird_image"      />   </LinearLayout>