代碼添加ProgressBar 進度條

    大家好 今天爲大家分享代碼中添加ProgressBar的例子 。當我們需要初始化程序或者聯網獲取數據 在數據庫中查找數據時，這些需要耗費些時間的操作就需要進度條來提示用戶有任務在進行，以免造成程序界面假死。 爲什麼要在代碼中添加而不在佈局裏面添加呢，因爲在代碼裏添加可以重複多次利用，免得沒用到時就得在佈局裏添加，麻煩。

    好了，下面我們來做個簡單的Demo熟悉一下，

    第一步：首先創建工程ProgressBarInsertLayoutinCode。

    第二步：創建XMl 佈局文件  我們就用自動創建的main.xml （在這裏面只添加了一個Button）用來啓動ProgressBar，代碼如下：

   <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/relative"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button android:id="@+id/button"
android:text="Click me"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</RelativeLayout>

        第三步：修改ProgressBarInsertLayoutinCodeActivity代碼，如下：（這裏我們用到了Handler和Thread，用來更新ProgressBar的進度，這樣就可以到一定是消除ProgressBar）

package cn.li.progressbardemo;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class ProgressBarInsertLayoutinCodeActivity extends Activity {
/** Called when the activity is first created. */
private Button btn;
private InsertProgressBar bar;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bar = new InsertProgressBar(ProgressBarInsertLayoutinCodeActivity.this);
btn = (Button)findViewById(R.id.button);
btn.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
bar.insertBar();
}
});
}
}

第四步：創建InsertProgressBar.java 此類創建了ProgressBar

package cn.li.progressbardemo;

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;
import android.widget.RelativeLayout.LayoutParams;

public class InsertProgressBar {

private RelativeLayout relative ;
private ProgressBar bar;
private ProgressBarInsertLayoutinCodeActivity context;
private int rate = 0;

protected static final int STOP = 0;
protected static final int NEXT = 1;

public InsertProgressBar(Context c) {
super();
context = (ProgressBarInsertLayoutinCodeActivity) c;
relative = (RelativeLayout)context.findViewById(R.id.relative);
bar = new ProgressBar(context);
//設置ProgressBar的高寬和顯示位置
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
params.getRules()[RelativeLayout.CENTER_IN_PARENT] = RelativeLayout.TRUE;
bar.setLayoutParams(params);
}

public void insertBar() {
bar.setProgress(0);
//當ProgressBar正在運行時就不再創建ProgressBar
if(!bar.isShown()){
bar.setVisibility(View.VISIBLE);
relative.addView(bar);
new MyThread().start();
}

}

class MyThread extends Thread{

@Override
public void run() {
super.run();

try {
for(int i=0;i<25;i++){
rate = (i+1)*4;
if(i!=24){
Message msg = new Message();
msg.what = NEXT;
myhandler.sendMessage(msg);
}else{
Message msg = new Message();
msg.what = STOP;
myhandler.sendMessage(msg);
}
MyThread.sleep(200);
}
} catch (Exception e) {
}

}

}
//創建一個Handle 接收消息
private Handler myhandler = new Handler(){

@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case STOP:
bar.setVisibility(View.GONE);
relative.removeView(bar);
Thread.currentThread().interrupt();
break;
case NEXT:
bar.setProgress(rate);
break;
}
} 
};
}

OK，運行工程 效果如圖