SeekBar調節圖檔透明度

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/text1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World."
        android:textColor="#ff0000"
        android:background="#00ff00"/>

    <EditText
        android:id="@+id/edit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="please enter your phone number"
        android:inputType="number"/>

    <ImageView
        android:id="@+id/image"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:src="@drawable/cat"/>
    <SeekBar
        android:id="@+id/sb"
        android:max="100"
        android:progress="30"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <ProgressBar
        android:id="@+id/pb"
        android:max="100"
        android:progress="30"
        style="?android:progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <RatingBar
        android:id="@+id/rb"
        android:numStars="5"
        android:max="10"
        android:progress="3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <RadioGroup
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <RadioButton
            android:id="@+id/rb1"
            android:checked="true"
            android:text="male"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
        <RadioButton
            android:id="@+id/rb2"
            android:text="female"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </RadioGroup>

    <CheckBox
        android:id="@+id/cb1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="football"/>
    <CheckBox
        android:id="@+id/cb2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="basketball"/>
    <CheckBox
        android:id="@+id/cb3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="baseball"/>

</LinearLayout>
           

MainActivity.java:

package com.miao.xxx;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.SeekBar;

public class MainActivity extends AppCompatActivity implements SeekBar.OnSeekBarChangeListener{
    private SeekBar sb;
    private ImageView image;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sb = (SeekBar)findViewById(R.id.sb);
        image = (ImageView)findViewById(R.id.image);
        image.setAlpha(1-sb.getProgress()/100.0f);
        sb.setOnSeekBarChangeListener(this);
    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        image.setAlpha(1-progress/100.0f);
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {

    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {

    }
}
           

設定圖檔透明度方法：image.setAlpha();