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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

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 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     <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.xml

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 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>
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.....***************

 

Android之ProgressBar初步应用