在 MapActivity (ESRI) 中显示 mmpk

Question

我是 Android 编程新手。 我编写了一个程序来在 ESRI mapview (100.7.0) 中显示 mmpk。当 mapview 在 MainActivity 中时，应用程序运行良好。 但是，当单击 MainActivity 中的按钮时，会调用 MapActivity 并导致应用崩溃。

请帮帮我

public class MainActivity extends AppCompatActivity {
     Button btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn=(Button)findViewById(R.id.button);
    }
    public void btnClick(View view) {
        Intent intent = new Intent(MainActivity.this,MapActivity.class);
        startActivity(intent);
    }
}

地图活动

public class MapActivity extends AppCompatActivity {

    private static final String TAG = MainActivity.class.getSimpleName();
    private static String extSDCardDirName;
    private static String filename;
    private static String mmpkFilePath;
    private MapView mMapView;
    private MobileMapPackage mapPackage;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // get the directory
        extSDCardDirName =Environment.getExternalStorageDirectory() + File.separator + "mmm/";
        // get mobile map package filename
        filename ="maps.mmpk";
        // create the full path to the mobile map package file
        mmpkFilePath = extSDCardDirName + filename;
        Log.d("FilePath", mmpkFilePath);
        // retrieve the MapView from layout
        mMapView = (MapView) findViewById(R.id.map);
        loadMobileMapPackage(mmpkFilePath);
    }
    private void loadMobileMapPackage(String mmpkFile) {
        // create the mobile map package
        mapPackage = new MobileMapPackage(mmpkFile);
        // load the mobile map package asynchronously
        mapPackage.loadAsync();
        // add done listener which will invoke when mobile map package has loaded
        mapPackage.addDoneLoadingListener(new Runnable() {
           @Override
            public void run() {
              // check load status and that the mobile map package has maps
               if (mapPackage.getLoadStatus() == LoadStatus.LOADED && !mapPackage.getMaps().isEmpty()) {
                // add the map from the mobile map package to the MapView
                mMapView.setMap(mapPackage.getMaps().get(0));
                mMapView.setAttributionTextVisible(false);
                //layer = new GraphicsLayer();
               } else {
                  // log an issue if the mobile map package fails to load
                  Log.e(TAG, mapPackage.getLoadError().getMessage());
               }
           }
      });

    }
}

错误：

04-15 12:00:43.653 7426-7426/com.mytest.mymap E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.mytest.mymap, PID: 7426
    java.lang.NullPointerException: Attempt to invoke virtual method 'void com.esri.arcgisruntime.mapping.view.MapView.setMap(com.esri.arcgisruntime.mapping.ArcGISMap)' on a null object reference
        at com.mytest.mymap.MapActivity$1.run(MapActivity.java:77)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:211)
        at android.app.ActivityThread.main(ActivityThread.java:5389)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)

当以下条件为真时，mapPackage 值不为空。

if (mapPackage.getLoadStatus() == LoadStatus.LOADED && !mapPackage.getMaps().isEmpty()) {
    // add the map from the mobile map package to the MapView
    mMapView.setMap(mapPackage.getMaps().get(0));
    mMapView.setAttributionTextVisible(false);
    //layer = new GraphicsLayer();
}

Answer 1

我的错误是将代码从 mainactivity 复制到 mapactivity !!!

 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

替换为

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_map);