你的位置:首页 > 操作系统

[操作系统]Android之ProgressBar初步应用


这里利用 ProgressBar 即时显示下载进度。

途中碰到的问题:

1、主线程中不能打开 URL、使用 Toast 等

2、子线程不能修改 UI

3、允许网络协议

4、暂停下载和继续下载

  ........

 

 

fragment_main 布局文件

 1 <RelativeLayout ="http://schemas.android.com/apk/res/android" 2   ="http://schemas.android.com/tools" 3   android:layout_width="match_parent" 4   android:layout_height="match_parent" 5   tools:context="com.dragon.android.textbar.MainActivity$PlaceholderFragment" > 6  7   <!-- prigressBar 进度条 --> 8   <!-- progress 当前进度 --> 9   <!-- indeterminate 不明确的  默认false -->10   <ProgressBar11     android:id="@+id/progressBar1"12     style="?android:attr/progressBarStyleHorizontal"13     android:layout_width="match_parent"14     android:layout_height="wrap_content"15     android:layout_centerInParent="true"16     android:max="100"17     android:progress="0"18     android:indeterminate="true"/>19 20   <Button21     android:id="@+id/button1"22     android:layout_width="wrap_content"23     android:layout_height="wrap_content"24     android:layout_alignParentTop="true"25     android:layout_centerHorizontal="true"26     android:onClick="startLoad"27     android:layout_marginTop="86dp"28     android:background="#009FEE"29     android:text="@string/start"30     android:textColor="#ffffff" />31 32   <TextView33     android:id="@+id/textView1"34     android:layout_width="wrap_content"35     android:layout_height="wrap_content"36     android:layout_above="@+id/progressBar1"37     android:background="@null"38     android:layout_alignParentLeft="true" />39   40 </RelativeLayout>

fragment_main

strings.

 1 <??> 2 <resources> 3  4   <string name="app_name">hwdownload</string> 5   <string name="hello_world">Hello world!</string> 6   <string name="action_settings">Settings</string> 7   <string name="start">开始</string> 8   <string name="stop">暂停</string> 9   <string name="contin">继续</string>10 11 </resources>

strings

(问题3)在 AndroidManifest 文件中配置

1 <!-- 请求网络权限 -->2   <uses-permission android:name="android.permission.INTERNET"/>

MainActivity(问题1、2)

package com.dragon.android.textbar;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.ProgressBar;import android.widget.TextView;import android.widget.Toast;/** * 只有创建一个 View 的线程才可以改变这个 View 的UI!!! 主线程也叫 UI 线程 */public class MainActivity extends Activity {  private ProgressBar progressBar1;  private Button button1;  private TextView textView1;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.fragment_main);    progressBar1 = (ProgressBar) findViewById(R.id.progressBar1);    button1 = (Button) findViewById(R.id.button1);    textView1 = (TextView) findViewById(R.id.textView1);  }  public void startLoad(View view) {     String text = (String) button1.getText();    // 设置按钮内容 ----并没有用...    button1.setText(text.equals(getResources().getString(R.string.start)) ? R.string.stop        : (text.equals(getResources().getString(R.string.stop)) ? R.string.contin            : R.string.stop));    progressBar1.setIndeterminate(false);    new Thread(new Runnable() {      private int percent;      @Override      public void run() {        try {          // 打开 URL 必须在子线程          URL url = new URL(              "http://b.zol-img.com.cn/sjbizhi/images/9/540x960/1472549276394.jpg");          HttpURLConnection conn = (HttpURLConnection) url.openConnection();          // conn.setRequestMethod("GET");          // conn.setReadTimeout(5000);          // conn.setConnectTimeout(5000);          int contentLength = conn.getContentLength();          if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {            InputStream is = conn.getInputStream();            byte[] buffer = new byte[1024];            int len = -1;            int sum = 0;            while ((len = is.read(buffer)) != -1) {              sum += len;              // 注意强转方式,防止一直为0              percent = (int) (100.0 * sum / contentLength);
// 在主线程上运行的子线程 runOnUiThread(new Runnable() { @Override public void run() { progressBar1.setProgress(percent); textView1.setText(percent + "%"); if (percent == progressBar1.getMax()) { Toast.makeText(MainActivity.this, "下载完成!", Toast.LENGTH_SHORT) .show(); } } }); } is.close(); conn.disconnect(); } } catch (IOException e) { e.printStackTrace(); } } }).start(); }}

**************然而并没有解决问题4,要用断点续传,但是还不会存放assets资源.....***************