一、activity_main.xml

        自定义了控件，外层是RelativeLayout，里面是个View，通过设置View的宽度来实现进度条的前进，主要com.jltxgcy.progressbar.ProgressView要和包名一致

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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=".MainActivity" >

    <com.jltxgcy.progressbar.ProgressView
        android:id="@+id/rootview"
        android:layout_width="match_parent"
        android:layout_height="15dp"
        android:background="#d6d6d6" >

        <View
            android:id="@+id/progress"
            android:layout_width="match_parent"
            android:layout_height="15dp" />
    </com.jltxgcy.progressbar.ProgressView>

</RelativeLayout>

       setProgress之所以要延迟20毫秒，是因为只有这样才能顺利获取View的高度和宽度。自定义控件可以操作自己的View，通过onFinishInflate，来找到View，然后来操作

package com.jltxgcy.progressbar;

import android.content.Context;
import android.graphics.Color;
import android.util.AttributeSet;
import android.view.View;
import android.widget.RelativeLayout;


public class ProgressView extends RelativeLayout {
	private View mProgress;

	public ProgressView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	@Override
	protected void onFinishInflate() {
		// TODO Auto-generated method stub
		super.onFinishInflate();
		mProgress = findViewById(R.id.progress);
	}

	public void setBackgroud() {
		mProgress.setBackgroundColor(Color.BLUE);
		
	}

	public void setProgress(final int progress) {
		postDelayed(new Runnable() {

			@Override
			public void run() {
				int width = getWidth();
				int height = getHeight();
				int curProgress = (int) (progress / 100.0 * width);
				LayoutParams params = new LayoutParams(curProgress, height);
				mProgress.setLayoutParams(params);
			}

		}, 20);

	}
}

       通过findViewById来操作自定义ProgreeView

package com.jltxgcy.progressbar;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {
	private ProgressView mProgressView;
	private int progressRate;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		mProgressView = (ProgressView) findViewById(R.id.rootview);
		
		mProgressView.postDelayed(new updataProgressBar(), 500);
		
	}
	
	class updataProgressBar implements Runnable{

		@Override
		public void run() {
			mProgressView.setBackgroud();
			mProgressView.setProgress(progressRate);
			progressRate += 2;
			mProgressView.postDelayed(new updataProgressBar(), 500);	
		}
	} 

}

Android 自定义ProgressBar