Android---31---SeekBar拖动条

通过拖动条来改变图片的透明度。

MainActivity.java：

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

public class MainActivity extends Activity implements OnSeekBarChangeListener {

	private ImageView imageView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		imageView = (ImageView) findViewById(R.id.image);
		SeekBar seekBar = (SeekBar) findViewById(R.id.seekbar);
		seekBar.setOnSeekBarChangeListener(this);
	}

	@Override
	public void onProgressChanged(SeekBar seekBar, int progress,
			boolean fromUser) {
		// TODO Auto-generated method stub
		imageView.setAlpha(progress);
	}

	@Override
	public void onStartTrackingTouch(SeekBar seekBar) {
		// TODO Auto-generated method stub

	}

	@Override
	public void onStopTrackingTouch(SeekBar seekBar) {
		// TODO Auto-generated method stub

	}

}

activity_main.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    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.example.seekbardemo.MainActivity" >

    <ImageView
        android:id="@+id/image"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:src="@drawable/Ghost Rider 04"
        />

    <SeekBar
        android:id="@+id/seekbar"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:max="255"
        android:progress="255"
        android:thumb="@drawable/ic_launcher" />

</LinearLayout>