Android 简明教程

Android Progress Bar using ProgressDialog

进度条用于显示某项任务的进度。例如，当您从互联网上上传或下载某些内容时，最好向用户显示此下载/上传进度。

Progress bars are used to show progress of a task. For example, when you are uploading or downloading something from the internet, it is better to show the progress of download/upload to the user.

在 Android 中，有一个名为 ProgressDialog 的类，允许您创建进度条。为了这样做，您需要实例化此类的对象。其语法为：

In android there is a class called ProgressDialog that allows you to create progress bar. In order to do this, you need to instantiate an object of this class. Its syntax is.

ProgressDialog progress = new ProgressDialog(this);

现在，您可以设置此对话框的某些属性。例如，其样式、其文本等。

Now you can set some properties of this dialog. Such as, its style, its text etc.

progress.setMessage("Downloading Music :) ");
progress.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progress.setIndeterminate(true);

除了这些方法之外， ProgressDialog 类还提供了其他方法。

Apart from these methods, there are other methods that are provided by the ProgressDialog class

Sr. No	Title & description
1	getMax() This method returns the maximum value of the progress.
2	incrementProgressBy(int diff) This method increments the progress bar by the difference of value passed as a parameter.
3	setIndeterminate(boolean indeterminate) This method sets the progress indicator as determinate or indeterminate.
4	setMax(int max) This method sets the maximum value of the progress dialog.
5	setProgress(int value) This method is used to update the progress dialog with some specific value.
6	show(Context context, CharSequence title, CharSequence message) This is a static method, used to display progress dialog.

Example

此示例演示了进度条（事实上就是进度条）的水平用法。按按钮时显示进度条。

This example demonstrates the horizontal use of the progress dialog which is in fact a progress bar. It display a progress bar on pressing the button.

要尝试此示例，您需要在按照以下步骤开发应用程序后，在实际设备上运行此示例。

To experiment with this example, you need to run this on an actual device after developing the application according to the steps below.

Steps	Description
1	You will use Android studio to create an Android application under a package com.example.sairamkrishna.myapplication.
2	Modify src/MainActivity.java file to add progress code to display the progress dialog.
3	Modify res/layout/activity_main.xml file to add respective XML code.
4	Run the application and choose a running android device and install the application on it and verify the results.

以下是修改后的主活动文件 src/MainActivity.java. 的内容

Following is the content of the modified main activity file src/MainActivity.java.

package com.example.sairamkrishna.myapplication;

import android.app.ProgressDialog;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends ActionBarActivity {
   Button b1;
   private ProgressDialog progress;

   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      b1 = (Button) findViewById(R.id.button2);
   }

   public void download(View view){
      progress=new ProgressDialog(this);
      progress.setMessage("Downloading Music");
      progress.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
      progress.setIndeterminate(true);
      progress.setProgress(0);
      progress.show();

      final int totalProgressTime = 100;
      final Thread t = new Thread() {
         @Override
         public void run() {
            int jumpTime = 0;

            while(jumpTime < totalProgressTime) {
               try {
                  sleep(200);
                  jumpTime += 5;
                  progress.setProgress(jumpTime);
               } catch (InterruptedException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
               }
            }
         }
      };
      t.start();
   }
}

将 res/layout/activity_main.xml 的内容修改为以下内容：

Modify the content of res/layout/activity_main.xml to the following −

<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:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/textView"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:textSize="30dp"
      android:text="Progress bar" />

   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorials Point"
      android:id="@+id/textView2"
      android:layout_below="@+id/textView"
      android:layout_centerHorizontal="true"
      android:textSize="35dp"
      android:textColor="#ff16ff01" />

   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Download"
      android:onClick="download"
      android:id="@+id/button2"
      android:layout_marginLeft="125dp"
      android:layout_marginStart="125dp"
      android:layout_centerVertical="true" />

</RelativeLayout>

这是默认 AndroidManifest.xml −

This is the default AndroidManifest.xml −

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.sairamkrishna.myapplication" >
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >

      <activity
         android:name=".MainActivity"
         android:label="@string/app_name" >

         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>

      </activity>

   </application>
</manifest>

我们尝试运行你的应用程序。我们假设你已经将实际的 Android 移动设备与计算机连接起来。若要从 Android 演播室运行该应用程序，请打开项目的一个活动文件，并单击工具栏中的“运行”图标。在启动你的应用程序之前，Android 演播室将显示以下窗口，让你选择要运行 Android 应用程序的位置。

Let’s try to run your application. We assume, you have connected your actual Android Mobile device with your computer. To run the app from Android studio, open one of your project’s activity files and click Run icon from the toolbar. Before starting your application, Android studio will display following window to select an option where you want to run your Android application.

选择你的移动设备作为选项，然后检查你的移动设备，它将显示以下屏幕 −

Select your mobile device as an option and then check your mobile device which will display following screen −

只需按下按钮即可启动进度条。按下后，将出现以下屏幕 -

Just press the button to start the Progress bar. After pressing, following screen would appear −

它会持续更新自身。

It will continuously update itself.