异步实现apk安装下载

在 Android 中，可以使用 `DownloadManager` 和 `InstallReferrerReceiver` 来实现异步下载和安装 APK 的功能。以下是一个简单的示例：

1. 下载 APK

DownloadManager downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(APK_URL));
request.setTitle("MyApp");
request.setDescription("Downloading MyApp");
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "MyApp.apk");
long downloadId = downloadManager.enqueue(request);

2. 安装 APK

public class InstallReferrerReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)) {
            long downloadId = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            if (downloadId != -1) {
                DownloadManager.Query query = new DownloadManager.Query();
                query.setFilterById(downloadId);
                Cursor cursor = downloadManager.query(query);
                if (cursor.moveToFirst()) {
                    int columnIndex = cursor.getColumnIndex(DownloadManager.COLUMN_STATUS);
                    if (cursor.getInt(columnIndex) == DownloadManager.STATUS_SUCCESSFUL) {
                        String uriString = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
                        Uri uri = Uri.parse(uriString);
                        Intent installIntent = new Intent(Intent.ACTION_VIEW);
                        installIntent.setDataAndType(uri, "application/vnd.android.package-archive");
                        installIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        context.startActivity(installIntent);
                    }
                }
            }
        }
    }
}

在 `AndroidManifest.xml` 中声明 `InstallReferrerReceiver`：

<receiver android:name=".InstallReferrerReceiver">
    <intent-filter>
        <action android:name="android.intent.action.DOWNLOAD_COMPLETE" />
    </intent-filter>
</receiver>

这样，当 APK 下载完成后，`InstallReferrerReceiver` 将会接收到 `ACTION_DOWNLOAD_COMPLETE` 的广播，并且执行安装 APK 的操作。需要注意的是，由于安装 APK 需要用户授权，因此需要在 `AndroidManifest.xml` 中声明 `android.permission.REQUEST_INSTALL_PACKAGES` 权限。