android - 如何将数据从一项 Activity 传输到另一项 Activity ？

Question

我正在尝试将数据从一个页面传输到另一个页面，但下面的代码出现了一些问题。我正在尝试使用 bundle 将变量的值从第一个 Activity 转移到第二个 Activity ，但出了点问题请告诉我出了什么问题。

下面是第一个 Activity :-

package route.planning;



import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;


public class login extends Activity {
    /** Called when the activity is first created. */

    Context mCtx;
    final static int START =0;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        mCtx = this;


        Button btn = (Button)findViewById(R.id.btn);

        btn.setOnClickListener(new OnClickListener(){

        //  @Override
        public void onClick(View v)
        {
            String fromLat = new String();
            String fromLong = new String();
            String toLat = new String();
            String toLong = new String();

            fromLat=String.valueOf(R.id.FromLatitude);
            fromLong=String.valueOf(R.id.FromLongitude);
            toLat=String.valueOf(R.id.ToLatitude);
            toLong=String.valueOf(R.id.ToLongitude);


            Intent intent = new Intent(mCtx, MapRouteActivity.class);

            /*Sending some arguments*/ 
            Bundle bundle = new Bundle();

              bundle.putString("fromLat",fromLat );
              bundle.putString("fromLong",fromLong );
              bundle.putString("toLat",toLat );
              bundle.putString("toLong",toLong );


              intent.putExtras(bundle);

            /*Start Activity*/
            mCtx.startActivity(intent);

            /*Start ActivityForResult*/
            ((Activity)mCtx).startActivityForResult(intent, 2);
        }
    });
    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        super.onActivityResult(requestCode, resultCode, data);

        if(requestCode == START)
        {

            Toast.makeText(mCtx, Integer.toString(resultCode), Toast.LENGTH_SHORT).show();
        }
    }


    @Override
    public void onDestroy(){
        super.onDestroy();
        finish();
    }
}

下面是第二个 Activity 的一部分，我试图从上面获取值(value)

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

import org.ci.geo.route.Road;
import org.ci.geo.route.RoadProvider;

import route.planning.R;

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.os.Bundle;
import android.os.Handler;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;

public class MapRouteActivity extends MapActivity {

        LinearLayout linearLayout;
        MapView mapView;
        private Road mRoad;

        @Override
        public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.routeplanning);
                mapView = (MapView) findViewById(R.id.mapview);
                mapView.setBuiltInZoomControls(true);

                Bundle extras = this.getIntent().getExtras();
                final String fLat=extras.getString("fromLat");
                final String fLong=extras.getString("fromLong");
                final String tLat=extras.getString("toLat");
                final String tLong=extras.getString("toLong");



                new Thread() {
                        @Override
                        public void run() {

                            double fromLat=Double.parseDouble(fLat);
                            double fromLon=Double.parseDouble(fLong);
                            double toLat=Double.parseDouble(tLat);
                            double toLon=Double.parseDouble(tLong);
                              //double fromLat = 28.6353, fromLon = 77.2250, toLat = 30.7313, toLon = 76.7754;
                                /***url contains the path to fetch the kml file from the internet*/
                                String url = RoadProvider
                                                .getUrl(fromLat, fromLon, toLat, toLon);
                                InputStream is = getConnection(url);
                                mRoad = RoadProvider.getRoute(is);
                                mHandler.sendEmptyMessage(0);
                        }
                }.start();
        }

Answer 1

        fromLat=String.valueOf(R.id.FromLatitude);
        fromLong=String.valueOf(R.id.FromLongitude);
        toLat=String.valueOf(R.id.ToLatitude);
        toLong=String.valueOf(R.id.ToLongitude);

问题来了。您不会从 Activity 中读取任何实际数据，但会获取控件标识符的字符串表示形式。

如果R.id.FromLatitude等是EditText的标识，需要获取用户输入:

fromLat = ((EditText)findViewById(R.id.FromLatitude)).getText().toString();