Android Implementation drag progress bar change picture transparency

Layout file:

1 <?XML version= "1.0" encoding= "Utf-8"?>2 <LinearLayoutxmlns: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= "@dimen/activity_vertical_margin"7 Android:paddingleft= "@dimen/activity_horizontal_margin"8 Android:paddingright= "@dimen/activity_horizontal_margin"9 Android:paddingtop= "@dimen/activity_vertical_margin"Ten Tools:context= "Com.hanqi.testapp2.PractiseActivity" One android:orientation= "vertical"> A  -     <SeekBar -         Android:layout_width= "Match_parent" the Android:layout_height= "Wrap_content" - Android:id= "@+id/sb_1" - Android:max= "255" //Set maximum progress to 255  - android:progress= "0"/> //Set initial progress to 0  +     <ImageView -         Android:layout_width= "Wrap_content" + Android:layout_height= "Wrap_content" A android:src= "@drawable/f4" at Android:id= "@+id/iv_1"/> - </LinearLayout>

Java Class Code:

1 Package com.hanqi.testapp2;2 3 import android.support.v7.app.AppCompatActivity;4 import Android.os.Bundle;5 import Android.widget.ImageView;6 import Android.widget.SeekBar;7 8 Public class Practiseactivity extends Appcompatactivity {9 Ten SeekBar sb_1; One ImageView iv_1; A @Override - protected void OnCreate (Bundle savedinstancestate) { - super.oncreate (savedinstancestate); the Setcontentview (r.layout.activity_practise); - sb_1 = (SeekBar) Findviewbyid (r.id.sb_1); - iv_1 = (ImageView) Findviewbyid (r.id.iv_1); - iv_1.setimagealpha (0); //This step is to set the start of the picture is transparent, do not set the picture will be displayed at the beginning of the run  + Sb_1.setonseekbarchangelistener (New Seekbar.onseekbarchangelistener () { - @Override + Public void Onprogresschanged (SeekBar SeekBar, int progress, Boolean fromuser) { A  at Iv_1.setimagealpha (progress); -             } -  - @Override - Public void Onstarttrackingtouch (SeekBar SeekBar) { -  in             } -  to @Override + Public void Onstoptrackingtouch (SeekBar SeekBar) { -  the             } *         }); $     }Panax Notoginseng}

The effect is:

Android Implementation drag progress bar change picture transparency