android开发分享Android中使用SeekBar拖动条实现改变图片透明度(代码实现)

  <?xml version="1.0" encoding="utf-8"?>  <linearlayout xmlns:android="https://schemas.android.com/apk/res/android"    xmlns:app="https://schemas.android.com/apk/res-auto"    xmlns:tools="https://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".seekbaractivity"    android:orientation="vertical">    <imageview      android:layout_width="match_parent"      android:id="@+id/image"      android:layout_height="250dp"      android:src="@drawable/dog"      />    <seekbar      android:layout_width="match_parent"      android:layout_height="wrap_content"      android:id="@+id/seekbar"      android:max="255"      android:progress="255"      />  </linearlayout>

  package com.badao.relativelayouttest;  import androidx.annotation.requiresapi;  import androidx.appcompat.app.appcompatactivity;  import android.os.build;  import android.os.bundle;  import android.widget.imageview;  import android.widget.seekbar;  public class seekbaractivity extends appcompatactivity {    private seekbar seekbar;    private imageview imageview;    @override    protected void oncreate(bundle savedinstancestate) {      super.oncreate(savedinstancestate);      setcontentview(r.layout.activity_seek_bar);      imageview = (imageview) findviewbyid(r.id.image);      seekbar = (seekbar) findviewbyid(r.id.seekbar);      seekbar.setonseekbarchangelistener(new seekbar.onseekbarchangelistener() {        @requiresapi(api = build.version_codes.jelly_bean)        @override        public void onprogresschanged(seekbar seekbar, int progress, boolean fromuser) {          imageview.setimagealpha(progress);        }        @override        public void onstarttrackingtouch(seekbar seekbar) {        }        @override        public void onstoptrackingtouch(seekbar seekbar) {        }      });    }  }