android中google“定位查询”

阅读更多 “定位查询”locate()方法，增加一个线程，在该线程中处理查询地点的功能，请参考代码清单16-10，完整代码请参考chapter16_7工程中src/com/work/map/MyMapActivity.java文件locate()方法代码部分。
【代码清单16-10】

/** * 定位查询 */private void locate() {LayoutInflater factory = LayoutInflater.from(MyMapActivity.this);View locationView = factory.inflate(R.layout.find_dialog, null);final EditText findText = (EditText) locationView.findViewById(R.id.dailog_find);new AlertDialog.Builder(this).setTitle(R.string.dialog_find).setView(locationView).setPositiveButton(R.string.button_ok,new DialogInterface.OnClickListener() {public void onClick(DialogInterface dialog, int whichButton) {findString = findText.getText().toString();progDialog = ProgressDialog.show(MyMapActivity.this,"处理中...", "定位" + findString, true, false);new Thread() {@Overridepublic void run() {try {Geocoder geocoder = new Geocoder(MyMapActivity.this);addresses = geocoder.getFromLocationName(findString, 1);if (addresses.size() > 0) {List overlayitems = new ArrayList();double lat = addresses.get(0).getLatitude();double lng = addresses.get(0).getLongitude();// 设定中心点centerPoit = new GeoPoint((int) (lat * 1E6),(int) (lng * 1E6)); // 地理坐标mc.setCenter(centerPoit);Log.i(TAG, " lat " + lat + "  lng "+ lng);int intMaxAddressLineIndex = addresses.get(0).getMaxAddressLineIndex();String address = "地址：";for (int j = 0; j <= intMaxAddressLineIndex; j++) {if (addresses.get(0) == null)continue;address += addresses.get(0).getAddressLine(j)+ ",";}if (address.endsWith(",")) {address = address.substring(0,address.length() - 1);}String title = "";if (addresses.get(0).getFeatureName() == null) {title = "";} else {title = addresses.get(0).getFeatureName();}overlayitems.add(new OverlayItem(centerPoit, title, address));Drawable marker = getResources().getDrawable(R.drawable.markermap2);locs = new LocationItemsOverlay(marker,overlayitems);handler.sendEmptyMessage(0);} else {handler.sendEmptyMessage(1);}} catch (Exception e) {e.printStackTrace();handler.sendEmptyMessage(1);}}}.start();}}).setNegativeButton(R.string.button_cancel,new DialogInterface.OnClickListener() {public void onClick(DialogInterface dialog, int which) {}}).show();}

通过下面的代码是实现显示进度条：
progDialog = ProgressDialog.show(MyMapActivity.this, "处理中...", "定位" + findString, true, false);
启动一个子线程，在该线程中实现地点查询，但是不能有更新UI的处理，如果查询成功调用handler.sendEmptyMessage(0)，如果失败调用handler.sendEmptyMessage(1)。
new Thread() {
@Override
public void run() {
… …
}
}.start();
在Hander的handleMessage方法中处理更新UI操作，其中成功(case 0)时候清除屏幕上原来的图层，重新添加图层，最后progDialog.dismiss()方法关闭进度条对话框。如果是查询失败(case 1)弹出Toast说明一下，也要通过progDialog.dismiss()方法关闭进度条对话框，否则进度条对话框不会关闭。

private Handler handler = new Handler() {@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case 0:mapView.getOverlays().clear();mapView.getOverlays().add(locs);progDialog.dismiss();break;case 1:Toast.makeText(MyMapActivity.this, "暂时无法" + findString + "信息。",Toast.LENGTH_SHORT).show();progDialog.dismiss();}}};

出自《Android开发案例驱动教程》第十六章

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