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，和只能在主线程中使用 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
<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"
tools:context="com.dragon.android.textbar.MainActivity$PlaceholderFragment" >
<!-- prigressBar 进度条 -->
<!-- progress 当前进度 -->
<!-- indeterminate 不明确的 默认false -->
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:max="100"
android:progress="0"
android:indeterminate="true"/>
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:onClick="startLoad"
android:layout_marginTop="86dp"
android:background="#009FEE"
android:text="@string/start"
android:textColor="#ffffff" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/progressBar1"
android:background="@null"
android:layout_alignParentLeft="true" />
</RelativeLayout>
strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">hwdownload</string>
<string name="hello_world">Hello world!</string>
<string name="action_settings">Settings</string>
<string name="start">开始</string>
<string name="stop">暂停</string>
<string name="contin">继续</string>
</resources>
（问题3）在 AndroidManifest 文件中配置
<!-- 请求网络权限 -->
<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;
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(
"/file/upload/202206/06/tc4f2q0s4i2.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.....***************
