我有以下布局文件。基本上我有谷歌地图，在左上角我有TextView我需要保持计数器说每15秒刷新一次地图。布局很好。
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:map="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/map"
tools:context="com.example.ns.appversion1.MapActivityFragment1"
android:name="com.google.android.gms.maps.SupportMapFragment"/>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:weightSum="2" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="left"
android:padding="3dp"
android:id="@+id/textRefresh"
android:background="@drawable/border"
android:text="Refreshing 1"
android:textColor="#03A9FA"
android:textSize="12sp" />
</LinearLayout>
</FrameLayout>
</RelativeLayout>
以下是我的代码。在视图函数中，我尝试实现Handler函数来保持计数器。因此，每隔15秒，我想调用JSON函数来检索最新的lat long值并相应地在地图上绘图。我现在停留在这里的第一步，它给出了我在内部类中无法访问变量timeleft，m_handlerTask和m_handler的错误？我想显示倒计时，以便用户在接下来的15秒钟内知道地图会刷新吗？
public class MapActivityFragment1 extends Fragment implements OnMapReadyCallback {
private GoogleMap mMap;
TextView tv;
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public MapActivityFragment1() {
// Required empty public constructor
}
// TODO: Rename and change types and number of parameters
public static MapActivityFragment1 newInstance(String param1, String param2) {
MapActivityFragment1 fragment = new MapActivityFragment1();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_map_activity_fragment1, null, false);
SupportMapFragment mapFragment = (SupportMapFragment) this.getChildFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
tv = (TextView) getActivity().findViewById(R.id.textRefresh);
Handler m_handler;
Runnable m_handlerTask ;
final int timeleft=15000;
final m_handler = new Handler();
final m_handlerTask = new Runnable()
{
@Override
public void run() {
if(timeleft>=0)
{
// do stuff
Log.i("timeleft",""+timeleft);
timeleft--;
tv.setText("Refreshing in "+timeleft);
}
else
{
m_handler.removeCallbacks(m_handlerTask); // cancel run
}
m_handler.postDelayed(m_handlerTask, 1000);
}
};
m_handlerTask.run();
return view;
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
public void onAttach(Context context) {
super.onAttach(context);
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
我尝试过Charu的解决方案如下。
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_map_activity_fragment1, null, false);
SupportMapFragment mapFragment = (SupportMapFragment) this.getChildFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
tv = (TextView) getActivity().findViewById(R.id.textRefresh);
MyCount counter = new MyCount(15000, 1000);
counter.start();
return view;
}
答案 0 :(得分：1)
这将演示从15到0的倒计时（-1秒），此任务将在每15秒后重复一次！
public class YourActivity extends Activity {
TextView textView;
android.os.Handler customHandler;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
textView = (TextView) findViewById(R.id.text);
customHandler = new android.os.Handler();
customHandler.postDelayed(updateTimerThread, 0);
}
// count down timer is an abstract class, so extend it and fill in methods
public class MyCount extends CountDownTimer {
public MyCount(long millisInFuture, long countDownInterval) {
super(millisInFuture, countDownInterval);
}
@Override
public void onFinish() {
textView.setText("done!");
}
@Override
public void onTick(long millisUntilFinished) {
textView.setText("Left: " + millisUntilFinished / 1000);
}
}
private Runnable updateTimerThread = new Runnable()
{
public void run()
{
// 10000 is the starting number (in milliseconds)
// 1000 is the number to count down each time (in milliseconds)
MyCount counter = new MyCount(15000, 1000);
counter.start();
customHandler.postDelayed(this, 15000); // repeat body after 15 seconds
}
};
}
答案 1 :(得分：0)
只是一个建议。
据我所知，处理程序在主线程上运行，因此，一旦此线程负责所有UI交互，请尝试使用轻量级处理任务。如果您需要处理大量数据或需要一些时间（例如，等待服务器的响应），建议您使用另一个线程，例如使用异步任务或协程。
我个人喜欢同时使用两者。我使用处理程序来创建此事件，现在是时候这样做了，我调用了在另一个线程中运行的函数来完成它。