java - 从另一个类获取 TextView

Question

我想显示这个 TextView “txtCalculate”，它来自 CustomerMapActivity 类，该类显示在另一个布局的 Activity_map_customer 布局中，该布局是 BonDeCommande 类的 Activity_bon_de_commande。问题是我不知道该怎么做我是java编程新手谢谢

    public void readValues(){

    DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
    Query lastQuery = ref.child("ride_info").orderByKey().limitToLast(1);
    lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            for(DataSnapshot ds : dataSnapshot.getChildren()){


                double value0_float = ds.child("pickup").child("lat").getValue(Double.class);
                double value1_float = ds.child("pickup").child("lng").getValue(Double.class);
                double value2_float = ds.child("destination").child("lat").getValue(Double.class);
                double value3_float = ds.child("destination").child("lng").getValue(Double.class);

                String pickupLat = String.valueOf(value0_float);
                String pickupLng = String.valueOf(value1_float);
                String destiLat = String.valueOf(value2_float);
                String destiLng = String.valueOf(value3_float);

                String requestUrl=null;
                try {
                    requestUrl = "https://maps.googleapis.com/maps/api/directions/json?"+
                            "mode=driving&"
                            +"transit_routing_preference=less_driving&"
                            +"origin="+pickupLat+","+pickupLng+"&"
                            +"destination="+destiLat+","+destiLng+"&"
                            +"key="+getResources().getString(R.string.google_maps_key);
                    Log.e("LINK",requestUrl);
                    mService.getPath(requestUrl).enqueue(new Callback<String>() {
                        @Override
                        public void onResponse(Call<String> call, Response<String> response) {
                            try {
                                JSONObject jsonObject = new JSONObject(response.body().toString());
                                JSONArray routes = jsonObject.getJSONArray("routes");

                                JSONObject object = routes.getJSONObject(0);
                                JSONArray legs = object.getJSONArray("legs");

                                JSONObject legsObject = legs.getJSONObject(0);

                                //Get distance
                                JSONObject distance = legsObject.getJSONObject("distance");
                                String distance_text = distance.getString("text");
                                //use regex to extract double from string
                                //This regex will remove all text not digit
                                Double distance_value= Double.parseDouble(distance_text.replaceAll("[^0-9\\\\.]+",""));

                                //Get Time
                                JSONObject time = legsObject.getJSONObject("duration");
                                String time_text = time.getString("text");
                                Integer time_value = Integer.parseInt(time_text.replaceAll("\\D+",""));

                                String final_calculate = String.format("%.2f €",
                                        TypeObject.getPrice(distance_value,time_value));

             HERE ----->        txtCalculate.setText(final_calculate);

                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onFailure(Call<String> call, Throwable t) {
                            mCurrentRide.cancelRide();
                            endRide();

                        }
                    });
                }
                catch (Exception ex)
                {
                    ex.printStackTrace();
                }
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            mCurrentRide.cancelRide();
            endRide();
        }
    });
}

我的屏幕截图

Answer 1

您需要创建一个带有更新方法的接口(interface)，在您的 Activity 中声明，然后将其作为参数传递给获取数据的处理程序对象。

不要忘记，如果您在不同的线程中获取数据，则需要始终在 UI 线程或主线程中更新 View 。

这里遵循一些示例代码:

您的 Activity 或 fragment

public class MainActivity extends AppCompatActivity
        implements UpdateViewCallback { // implement the interface here

    private TextView textView = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        textView = findViewById(R.id.textView);

        // Pass the interface in your Object that makes the async work
        final AsyncWork asyncWork = new AsyncWork(this);

        // Running
        Thread thread = new Thread(asyncWork);
        thread.start();
    }

    /**
     * UpdateViewCallback
     * @param result
     */
    @Override
    public void updateView(final String result) {
        // Always update View on MainThread or an UI Thread, or else issues will start to happening
        this.runOnUiThread(new Runnable() {
            public void run() {
                // Check if View is null since you're updating in a thread async
                if (textView != null) {
                    textView.setText(result);
                }
            }
        });
    }

}

您的界面:

public interface UpdateViewCallback {
    void updateView(String result);
}

处理异步工作的对象:

public class AsyncWork implements Runnable {

    private  UpdateViewCallback updateViewCallback;

    public AsyncWork(UpdateViewCallback updateViewCallback) {
        this.updateViewCallback = updateViewCallback;
    }

    /**
     * Async Work here
     */
    @Override
    public void run() {
        // Do some Work and after update using the interface you passed in the constructor
        updateViewCallback.updateView("This is a test");
    }
}