android中google“定位查询”

“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() {
							@Override
							public void run() {
								try {
									Geocoder geocoder = new Geocoder(
											MyMapActivity.this);
									addresses = geocoder.getFromLocationName(
											findString, 1);

									if (addresses.size() > 0) {
								List<OverlayItem> overlayitems = new ArrayList<OverlayItem>();
										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() {

		@Override
		public 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