用SeekBar控制图片的透明度

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context="com.hanqi.testapp2.TestActivity4"
    android:orientation="vertical">

    <ProgressBar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        style="?android:attr/progressBarStyleHorizontal"
        android:progress="0"
        android:secondaryProgress="0"
        android:max="80"
        android:id="@+id/pb_1"/>

    <ProgressBar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        style="?android:attr/progressBarStyleLarge"
        android:id="@+id/pb_2"/>

    <SeekBar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:progress="0"
        android:max="80"
        android:secondaryProgress="0"
        android:id="@+id/se_1"/>

    <RatingBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:numStars="5"
        android:rating="3.5"
        android:isIndicator="true"/>

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/xiao3"
        android:alpha="1"
        android:id="@+id/iv_1"/>

    <SeekBar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:progress="0"
        android:secondaryProgress="0"
        android:max="200"
        android:id="@+id/se_2"/>

</LinearLayout>

package com.hanqi.testapp2;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.SeekBar;

public class TestActivity4 extends AppCompatActivity {

    SeekBar se_1;

    ProgressBar pb_1;
    ProgressBar pb_2;
    SeekBar se_2;
    ImageView iv_1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test4);

        se_1=(SeekBar)findViewById(R.id.se_1);
        pb_1=(ProgressBar)findViewById(R.id.pb_1);
        pb_2=(ProgressBar)findViewById(R.id.pb_2);
        se_2=(SeekBar)findViewById(R.id.se_2);
        iv_1=(ImageView)findViewById(R.id.iv_1);
        iv_1.setAlpha(0);

       // AlertDialog ad=new AlertDialog.Builder(this).create();

        se_1.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

            //进度变化触发
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

                //设置进度条1的进度值
                pb_1.setProgress(progress);

                //判断是否达到最大值
                if(progress==se_1.getMax())
                {
                    pb_2.setVisibility(View.INVISIBLE);//不显示但是位置还保留
                }
                else
                {
                    pb_2.setVisibility(View.VISIBLE);
                }

                //只要progress变化就被触发

                //Toast.makeText(TestActivity4.this, "当前进度="+progress, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

                Log.e("TAG","进度条开始拖动");
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

                Log.e("TAG","进度条停止拖动");
            }
        });

        se_2.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

            iv_1.setAlpha(progress);

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

                Log.e("TAG","进度条开始拖动");

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

                Log.e("TAG","进度条停止拖动");

            }
        });
    }
}