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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 xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="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 <ProgressBar 11 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 <Button 21 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 <TextView 33 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>
strings.xml
1 <?xml version="1.0" encoding="utf-8"?> 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>
（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.....***************
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原文地址：http://www.cnblogs.com/xmcx1995/p/5831774.html
