插一张图片,用SeekBar来控制图片的透明度

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     xmlns:tools="http://schemas.android.com/tools"
 4     android:layout_width="match_parent"
 5     android:layout_height="match_parent"
 6     android:paddingBottom="16dp"
 7     android:paddingLeft="16dp"
 8     android:paddingRight="16dp"
 9     android:paddingTop="16dp"
10     tools:context="com.example.wang.testapp2.TestActivity4"
11     android:orientation="vertical">
12 
13     <ImageView
14         android:layout_width="match_parent"
15         android:layout_height="200dp"
16         android:src="@drawable/car"
17         android:id="@+id/iv_1" />
18 
19     <SeekBar
20         android:layout_width="match_parent"
21         android:layout_height="wrap_content"
22         android:progress="0"
23         android:max="255"
24         android:id="@+id/se_2"/>
25 </LinearLayout>

 1 package com.example.wang.testapp2;
 2 
 3 import android.app.Activity;
 4 import android.app.AlertDialog;
 5 import android.support.v7.app.AppCompatActivity;
 6 import android.os.Bundle;
 7 import android.util.Log;
 8 import android.view.View;
 9 import android.widget.ImageView;
10 import android.widget.ProgressBar;
11 import android.widget.SeekBar;
12 import android.widget.Toast;
13 
14 public class TestActivity4 extends Activity {
15 
16     SeekBar se_2;
17     ImageView iv_1;
18 
19     @Override
20     protected void onCreate(Bundle savedInstanceState) {
21         super.onCreate(savedInstanceState);
22         setContentView(R.layout.activity_test4);
23 
24         se_2=(SeekBar)findViewById(R.id.se_2);
25         iv_1=(ImageView)findViewById(R.id.iv_1);
26 
27 
28         //插一张图片 用SeekBar来控制图片的透明度
29 
30 //        iv_1.setImageAlpha(1);
31 
32         iv_1.setAlpha(1);
33 
34         se_2.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
35             @Override
36             public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
37 
38 //                iv_1.setImageAlpha(progress);
39 
40                 iv_1.setAlpha(progress);
41             }
42 
43             @Override
44             public void onStartTrackingTouch(SeekBar seekBar) {
45 
46 
47 
48             }
49 
50             @Override
51             public void onStopTrackingTouch(SeekBar seekBar) {
52 
53 
54             }
55         });
56 
57     }
58 }