Android - Download(下载) 项目详解

Download(下载) 项目详解

本文地址: http://blog.csdn.net/caroline_wendy/article/details/22280461

本文的合集已经编著成书，《高级Android开发强化实战》，欢迎各位读友的建议和指导。

在京东即可购买：https://item.jd.com/12385680.html

环境: Android 0.5.2 + gradle 1.11 + kindle fire

Download, 下载项目, 从Internet上下载资源, 并存入本地SD卡.

点击Download按钮, 下载图片, 然后显示下载内容, 可以点击查看.

Download的具体设计:

1. 修改activity_main.xml

位置: res->layout->activity_main.xml

<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="mzx.spike.download.app.MainActivity"><Buttonandroid:id="@+id/download_button"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="Download"/><TextViewandroid:text="@string/hello_world"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_below="@id/download_button" /></RelativeLayout>

添加一个按钮(Button) , 使"hello_world"在其下方, 使用 layout_below 属性;

2. 修改AndroidManifest.xml

位置: main->AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="mzx.spike.download.app" ><uses-permission android:name="android.permission.INTERNET"/><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/><applicationandroid:allowBackup="true"android:icon="@drawable/ic_launcher"android:label="@string/app_name"android:theme="@style/AppTheme" ><activityandroid:name="mzx.spike.download.app.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>

需要INTERNET, 连接互联网的权限; WRITE_EXTERNAL_STORAGE, 写入存储器的权限;

3. 修改MainActivity.java

位置: java->package->MainActivity.java

package mzx.spike.download.app;import android.app.Activity;
import android.app.DownloadManager;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;public class MainActivity extends Activity {private static final String TAG = "Download";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button buttonDownload = (Button)findViewById(R.id.download_button);buttonDownload.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {myDownload();}});}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {// Handle action bar item clicks here. The action bar will// automatically handle clicks on the Home/Up button, so long// as you specify a parent activity in AndroidManifest.xml.int id = item.getItemId();if (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}private void myDownload() {String serviceString = Context.DOWNLOAD_SERVICE;DownloadManager downloadManager;downloadManager = (DownloadManager) getSystemService(serviceString);Uri uri = Uri.parse("http://bizhi.zhuoku.com/2014/03/26/TAHITI/TAHITI02.jpg");DownloadManager.Request request = new DownloadManager.Request(uri);request.setDestinationInExternalPublicDir("/Download", "file.jpg");request.setVisibleInDownloadsUi(true);long reference = downloadManager.enqueue(request);Log.d(TAG, "Download Reference: " + reference);Cursor c = downloadManager.query(new DownloadManager.Query().setFilterById(reference));if (c == null) {Toast.makeText(this, "Download not found!", Toast.LENGTH_LONG).show();} else {c.moveToFirst();Log.d(getClass().getName(), "Column_id : " +c.getLong(c.getColumnIndex(DownloadManager.COLUMN_ID)));Log.d(getClass().getName(), "Column_bytes_downloaded so far : " +c.getLong(c.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR)));Log.d(getClass().getName(), "Column last modified timestamp : " +c.getLong(c.getColumnIndex(DownloadManager.COLUMN_LAST_MODIFIED_TIMESTAMP)));Log.d(getClass().getName(), "Column local uri : " +c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI)));Log.d(getClass().getName(), "Column statue : " +c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS)));Log.d(getClass().getName(), "Column reason : " +c.getInt(c.getColumnIndex(DownloadManager.COLUMN_REASON)));Toast.makeText(this, statusMessage(c), Toast.LENGTH_LONG).show();}startActivity(new Intent(DownloadManager.ACTION_VIEW_DOWNLOADS));}private String statusMessage(Cursor c){switch(c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS))){case DownloadManager.STATUS_FAILED:return "Download failed";case DownloadManager.STATUS_PAUSED:return "Download paused";case DownloadManager.STATUS_PENDING:return "Download pending";case DownloadManager.STATUS_RUNNING:return "Download in progress!";case DownloadManager.STATUS_SUCCESSFUL:return "Download finished";default:return "Unknown Information";}}}

详解:

1. 在创建界面中, 填写按钮(button)的点击事件(setOnClickListener), 触发下载方法(myDownload);

2. DownloadManager 获取下载的服务(Context.DOWNLOAD_SERVICE);

3. 设置下载的链接(uri), 设置存储位置(setDestinationInExternalPublicDir), 显示下载用户接口(setVisibleInDownloadsUi);

4. 放置下载队列, 开始下载, downloadManager.enqueue(request);

5. 通过游标获取下载信息, downloadManager.query();

6. 输出相应的下载信息(COLUMN_*), 和下载状态(STATUS_*);

7. 显示下载视图(DownloadManager.ACTION_VIEW_DOWNLOADS);

注意:

存储位置(setDestinationInExternalPublicDir), 需要提前设置, 否则无法查看文件, 存储至content位置;

4. 运行程序

下载地址: http://download.csdn.net/detail/u012515223/7106567