Android面试题之Progress控件通过10秒的时间完成进度显示

Posted 2023-02-23 wjinhhua

实现的思路比较多，可以用线程实现，网上比较多用线程实现的例子，本文通过Handler来实现，具体代码如下：

xml代码

<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="com.ft626.interviewtest.MainActivity" >
    <ProgressBar
        android:id="@+id/pb"
        android:layout_width="match_parent"
        android:layout_height="5dp"
        android:progress="0"
        style="?android:attr/progressBarStyleHorizontal" />
    <TextView
        android:id="@+id/tv_progress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/tv_progress"
        android:layout_alignParentRight="true"/>
 <Button 
        android:id="@+id/bt_start"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tv_progress"
        android:text="开始计算进度"
        />
</RelativeLayout>

java代码（代码比较简单，就不添加注释了

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MainActivity extends Activity 

    private ProgressBar pb;
    private TextView tv_progress;
    private Button bt_start;


    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        initData();
    

    private Handler handler = new Handler()
        public void handleMessage(android.os.Message msg) 
            if (msg.what == MSG_UPDATE) 
                int pp = pb.getProgress();
                if (pp<100)  
                    pp++;
                    handler.sendEmptyMessageDelayed(MSG_UPDATE, 100);
                 else 
                    handler.removeMessages(MSG_UPDATE);
                
                pb.setProgress(pp);  
                tv_progress.setText(pp+"%");
            
        ;
    ;

    private void initView() 
        pb = (ProgressBar) this.findViewById(R.id.pb);
        tv_progress = (TextView) this.findViewById(R.id.tv_progress);
        bt_start = (Button) this.findViewById(R.id.bt_start);
    

    private static final int MSG_UPDATE = 0x100;
    private void initData() 
        pb.setMax(100);
        pb.setProgress(0);
        bt_start.setOnClickListener(new OnClickListener() 

            @Override
            public void onClick(View v) 
                handler.sendEmptyMessage(MSG_UPDATE);
            
        );
    

当然，随后还要在onDestory()方法把Handler置空，防止内存泄漏，笔者就不贴代码了。。。