当react-native项目中有版本更新需求时，android会用到下载新版本需求，此时，可以通过封装Native Modules 去调用android原生DownloadManager来实现下载，
1、书写功能类继承ReactContextBaseJavaModule，用于将方法暴露给js调用，程序中值得注意的地方是通过getCurrentActivity()来获取上下Context,而不是直接new Activity,若是直接new出来的实例是无法调用request.setDestinationInExternalFilesDir(xxx,xxx,xxx)，此处会报错。
package com.testnativemodule;
import android.app.DownloadManager;
import android.app.DownloadManager.Request;
import android.content.Context;
import android.app.Activity;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Environment;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;
public class DownloadApk extends ReactContextBaseJavaModule{
DownloadManager downManager ;
Activity myActivity;
public DownloadApk(ReactApplicationContext reactContext) {
super(reactContext);
}
@Override
public String getName(){
return "DownloadApk";
}
@ReactMethod
public void downloading(String url,String description){
myActivity =getCurrentActivity();
downManager = (DownloadManager)myActivity.getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse(url);
DownloadManager.Request request = new Request(uri);
request.setAllowedNetworkTypes(Request.NETWORK_WIFI);
//设置通知栏标题
request.setNotificationVisibility(Request.VISIBILITY_VISIBLE);
request.setMimeType("application/vnd.android.package-archive");
request.setTitle("下载");
if(description==null||"".equals(description)){
description="目标apk正在下载";
}
request.setDescription(description);
request.setAllowedOverRoaming(false);
//设置文件存放目录
request.setDestinationInExternalFilesDir(myActivity, Environment.DIRECTORY_DOWNLOADS, description);
long downloadid=downManager.enqueue(request);
SharedPreferences sPreferences = myActivity.getSharedPreferences("ggfw_download", 0);
sPreferences.edit().putLong("ggfw_download_apk", downloadid).commit();
}
}
2、书写类继承ReactPackage接口，用于注册Native Modules，使得js上能够引入调用。
package com.testnativemodule;importcom.facebook.react.ReactPackage;importcom.facebook.react.bridge.JavaScriptModule;importcom.facebook.react.bridge.NativeModule;importcom.facebook.react.bridge.ReactApplicationContext;importcom.facebook.react.uimanager.ViewManager;importjava.util.ArrayList;importjava.util.Collections;importjava.util.List;public class DownloadApkPackage implementsReactPackage{@OverridepublicListcreateNativeModules(ReactApplicationContextreactContext){ Listmodules=newArrayList<>(); modules.add(newDownloadApk(reactContext)); returnmodules; }@OverridepublicList>createJSModules(){returnCollections.emptyList(); }@OverridepublicListcreateViewManagers(ReactApplicationContext reactContext) {
return Collections.emptyList();
}
}
以上两个类已经实现了基本的下载功能，需要丰富下载其他逻辑如暂停，开始，等，DownLoadManager可以很好的实现，此处不对该类功能深入分析，网络上有很多的文章介绍它。
而外的一个功能，当下载完后，希望直接调用打开apk的安装界面，可以通过广播监听下载完成事件来实现。当监听到事件，判断服务下载的是否是我们所需的下载，是则进行打开安装界面：
3.我们可以写个类继承BroadcastReceiver，此处要注意的是使用Uri.fromFile(file)来取得下载文件的uri,网上有资料说dManager.getUriForDownloadedFile(myDwonloadID)来获取uri,但是此处使用却会使得程序本科，查看logcat日志信息描述大概为，找不到能够处理application/vnd.android.package-archive的Activity,后来发现应该是dManager.getUriForDownloadedFile返回的uri应该不是能够被正确指向下载文件的，具体原因我不是很清楚，故换了种方式来取得文件uri.
package com.testnativemodule;
import android.app.DownloadManager;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.net.Uri;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast;
import java.io.File;
/**
* Created by audaque on 2016/9/6.
*/
public class DownLoadBroadcastReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
long myDwonloadID = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
SharedPreferences sPreferences = context.getSharedPreferences("ggfw_download", 0);
long refernece = sPreferences.getLong("ggfw_download_apk", 0);
if (refernece == myDwonloadID) {
DownloadManager dManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
Intent install = new Intent(Intent.ACTION_VIEW);
// Uri downloadFileUri = dManager.getUriForDownloadedFile(myDwonloadID);
DownloadManager.Query querybyId = new DownloadManager.Query();
querybyId.setFilterById(myDwonloadID);
Cursor myDownload = dManager.query(querybyId);
String dolownname=null;
if(myDownload.moveToFirst()){
int status = myDownload.getInt(myDownload.getColumnIndex(DownloadManager.COLUMN_STATUS));
if (status == DownloadManager.STATUS_SUCCESSFUL) {
// process download
int fileNameIdx = myDownload.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME);
//此处取得的是完整路径+文件名称
dolownname=myDownload.getString(fileNameIdx);
}else{
Toast.makeText(context,"下载失败，删除残留文件",Toast.LENGTH_LONG).show();
dManager.remove(myDwonloadID);
myDownload.close();
return;
}
myDownload.close();
}
if(dolownname==null){
return;
}
File file = new File(dolownname);
install.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
install.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.getApplicationContext().startActivity(install);
}
}
}
记得在AndroidManifest.xml中注册广播监听配置：
<receiver android:name="com.testnativemodule.DownLoadBroadcastReceiver">
<intent-filter>
<action android:name="android.intent.action.DOWNLOAD_COMPLETE"/>
</intent-filter>
</receiver>
以上完成基本的下载功能，并下载完成后打开apk安装界面。
在js中引入NativeModules，通过其调用方式如下：
import {NativeModules} from 'react-native';
NativeModules.DownloadApk.downloading("http://len51-website.oss-cn-shenzhen.aliyuncs.com/app%2FSuiShoujie.apk","suishoujie.apk");
参数一为下载地址中的apk,下载保存文件名为第二个参数值suishoujie.apk。
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