尝试安卓端加载离线地图，下载了使用osmdroid的离线版项目源码，更改JDK环境、gradle环境，一顿操作下来，踉踉跄跄的把程序跑起来了，但是离线的地图一直加载不出来。给我整emo了，先记录分享出来，看有没有和我一样别的盆友，一起探讨下。
我尝试了4种办法，目前只有第4种方法，使用 OfflineTileProvider类，才加载出来

源码下载

• 项目的地址在这里：项目地址
• 源码说明：原项目的gradle版本2.5，gradle的构建版本是3.1.2，目标sdk版本是28
  项目比较老，构建工具比较老，原项目配置下无法完成构建，我做了修改,在环境配置节
• 使用的osmdroid安卓库是4.3implementation 'org.osmdroid:osmdroid-android:4.3'

环境配置

主要做了三处的修改

1. 工程的build.gradle文件中仓库替换了国内的源

maven { url 'https://maven.aliyun.com/repository/google'}
maven { url 'https://maven.aliyun.com/repository/public'}
maven { url 'https://maven.aliyun.com/repository/jcenter'}

2. 工程的build.gradle文件中更改了gradle构建版本

dependencies {classpath 'com.android.tools.build:gradle:7.4.2'
}

3. 修改了gradle-wrapper.properties的distributionUrl

distributionUrl=https\://services.gradle.org/distributions/gradle-7.5-bin.zip

尝试不同离线加载

尝试了四个项目，第一个和第二个日志里都有okhttp网络请求的报错，都会尝试去下载瓦片。
第四个尝试，有点特殊，他用到了OfflineTileProvider类，最后一个测试成功了。

1. 尝试1：原项目，启动成功，无法加载离线的瓦片，源码项目参考Using OSMDroid for Offline mapping in Android, step-by-step

• 说明：没有使用Provider直接给mapView设置 mapView.setTileSource(TileSourceFactory.MAPQUESTOSM);

2. 尝试2：另外一个项目OSMOfflineMap-Android

• 说明：用MapTileModuleProviderBase类结合 XYTileSource类，也是运行成功，没跑起来

3. 尝试3：参考Android使用osmdroid加载在线地图，离线地图以及各种填坑姿势

• 说明1：MapTileModuleProviderBase类结合 自定义CustomTileSource类继承BitmapTileSourceBase类
• 说明2：用的osmdroid版本是implementation 'org.osmdroid:osmdroid-android:6.1.11'使用kotlin写，我用Java翻译了一下，也没有加载出地图瓦片

 public void mapViewOtherData0(MapView mapView){String strFilepath = copyAssetGetFilePath("tiles.zip");File exitFile =new File(strFilepath);if(!exitFile.exists()){System.out.println("文件不存在！");}else {try{// 获取解压后的文件夹名称String source = exitFile.getName().substring(0, exitFile.getName().lastIndexOf("."));// 创建归档文件对象数组IArchiveFile[] archives = new IArchiveFile[1];archives[0] =ArchiveFileFactory.getArchiveFile(exitFile);// 创建 CustomTileSource 对象CustomTileSource customTiles = new CustomTileSource(source , 1, 13, 256, ".png");// 创建一个大小为1的 MapTileModuleProviderBase 数组MapTileModuleProviderBase[] providers = new MapTileModuleProviderBase[1];providers[0] =new MapTileFileArchiveProvider(new SimpleRegisterReceiver(this),customTiles,archives);MapTileProviderArray tileProvider = new MapTileProviderArray(customTiles,new SimpleRegisterReceiver(this),providers);TilesOverlay tilesOverlay = new TilesOverlay(tileProvider,this);tilesOverlay.setLoadingBackgroundColor(Color.TRANSPARENT);mapView.getOverlayManager().add(tilesOverlay);IMapController mapViewController = mapView.getController();mapViewController.setZoom(10);
//        mapViewController.setCenter(BERLIN);}catch (Exception e){e.printStackTrace();}}}
private String copyAssetGetFilePath(String fileName) {try {File cacheDir = getApplicationContext().getCacheDir();if (!cacheDir.exists()) {cacheDir.mkdirs();}File outFile = new File(cacheDir, fileName);if (!outFile.exists()) {boolean res = outFile.createNewFile();if (!res) {return null;}} else {if (outFile.length() > 10) {//表示已经写入一次return outFile.getPath();}}InputStream is = getApplicationContext().getAssets().open(fileName);FileOutputStream fos = new FileOutputStream(outFile);byte[] buffer = new byte[1024];int byteCount;while ((byteCount = is.read(buffer)) != -1) {fos.write(buffer, 0, byteCount);}fos.flush();is.close();fos.close();return outFile.getPath();} catch (IOException e) {e.printStackTrace();}return null;}

报错信息

E Please configure a relevant user agent; current value is: osmdroid

4. 尝试4：android osmdroid 加载常用离线地图格式（开源的在线地图），这个博客使用的mbtiles，目前还在下载中，可用图新地球下载，也可以直接用tiles.zip，已测试

• 说明：使用OfflineTileProvider类

public void mapViewOtherData(MapView mapView){
//        String strFilepath = Environment.getExternalStorageDirectory().getPath() + "/njmap_DarkBlue.mbtiles";String strFilepath = copyAssetGetFilePath("tiles.zip");File exitFile =new File(strFilepath);
//        File exitFile = new File(strFilepath);String fileName = "tiles.zip";if (!exitFile.exists()) {mapView.setTileSource(TileSourceFactory.MAPNIK);}else {fileName = fileName.substring(fileName.lastIndexOf(".") + 1);if (fileName.length() == 0)return;if (ArchiveFileFactory.isFileExtensionRegistered(fileName)) {try {OfflineTileProvider tileProvider = new OfflineTileProvider((IRegisterReceiver) new SimpleRegisterReceiver(this), new File[] { exitFile });mapView.setTileProvider(tileProvider);String source = "";IArchiveFile[] archives = tileProvider.getArchives();if (archives.length > 0) {Set<String> tileSources = archives[0].getTileSources();if (!tileSources.isEmpty()) {source = tileSources.iterator().next();mapView.setTileSource(FileBasedTileSource.getSource(source));} else {mapView.setTileSource(TileSourceFactory.DEFAULT_TILE_SOURCE);}} elsemapView.setTileSource(TileSourceFactory.DEFAULT_TILE_SOURCE);Toast.makeText(this,"Using " + exitFile.getAbsolutePath() + " "+ source, Toast.LENGTH_LONG).show();mapView.invalidate();return;} catch (Exception ex) {ex.printStackTrace();}Toast.makeText(this,  " did not have any files I can open! Try using MOBAC", Toast.LENGTH_LONG).show();} else{Toast.makeText(this, " dir not found!", Toast.LENGTH_LONG).show();}}}

遇到的问题

android:exported needs to be explicitly specified for element <activity#com.example.android.osmdroidofflinedemo.MainActivity>. Apps targeting Android 12 and higher are required to specify an explicit value for `android:exported` when the corresponding component has an intent filter defined. See https://developer.android.com/guide/topics/manifest/activity-element#exported for details. 

办法在此：tools:node="merge"参考