我是android的新手,我有一个问题。我想在单击按钮时将for(或while)循环中的变量“ adresa”发送到另一个活动,但是始终从循环中发送最后一个值。
这是代码:
PS。对不起我的英语不好
这是第一次活动

package com.example.locationtracker;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.app.ActionBar.LayoutParams;
import android.widget.LinearLayout;
import android.widget.Toast;
import android.widget.Button;

public class DatabasesActivity extends Activity {

public static String adresa;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {


    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    final DBAdapter2 db = new DBAdapter2(this);



    //---get a posao---
    db.open();
    final Cursor c = db.getPosao(0);

    if (c.moveToFirst()){

        final int x = 0;
        final LinearLayout lm = (LinearLayout) findViewById(R.id.linearMain);
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
//          while (c.moveToNext()) {
        for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {


            LinearLayout ll = new LinearLayout(this);
            ll.setOrientation(LinearLayout.HORIZONTAL);
            final Button button = new Button(this) ;

            button.setId(x+1);
            button.setText("id: " + c.getString(0) + "\n" +
                    "Ime: " + c.getString(1) + "\n" +
                    "Adresa: " + c.getString(2) + "\n" +
                    "Telefon: " + c.getString(3) + "\n" +
                    "Napomena: " + c.getString(4) + "\n" +
                    "Status:  " + c.getString(5));
            button.setLayoutParams(params);

            adresa = c.getString(2);

            button.setOnClickListener(new OnClickListener() {
                public void onClick(View v) {
                    // Perform action on click
                    Intent activityChangeIntent = new Intent(DatabasesActivity.this, PrikazMape.class);
                    activityChangeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    activityChangeIntent.putExtra("add", adresa);

                   DatabasesActivity.this.startActivity(activityChangeIntent);
                }
            });
          //Add button to LinearLayout
            ll.addView(button);
           //Add button to LinearLayout defined in XML
            lm.addView(ll);
        }
    }



    else
        Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show();
    db.close();


    try {
        String destPath = "/data/data/" + getPackageName() +
            "/databases";
        File f = new File(destPath);
        if (!f.exists()) {
            f.mkdirs();
            f.createNewFile();

            //---copy the db from the assets folder into
            // the databases folder---
            CopyDB(getBaseContext().getAssets().open("mydb"),
                new FileOutputStream(destPath + "/MyDB"));
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void CopyDB(InputStream inputStream,
OutputStream outputStream) throws IOException {
    //---copy 1K bytes at a time---
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) > 0) {
        outputStream.write(buffer, 0, length);
    }
    inputStream.close();
    outputStream.close();
}


}


第二

package com.example.locationtracker;

import java.io.IOException;
import java.util.List;
import java.util.Locale;

import com.google.android.gms.maps.*;
import com.google.android.gms.maps.model.*;

import android.app.Activity;
import android.content.Intent;
import android.location.Address;
import android.location.Geocoder;
import android.os.Bundle;

public class PrikazMape extends Activity {

double latitude;
double longtitude;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.map_activity);



    Intent mInt = getIntent();
    String adresa = mInt.getStringExtra("add");


    Geocoder geoCoder = new Geocoder(PrikazMape.this);

    try {
        List<Address> addresses =
    geoCoder.getFromLocationName(adresa, 1);
        if (addresses.size() >  0) {
            latitude = addresses.get(0).getLatitude();
            longtitude = addresses.get(0).getLongitude(); }

    } catch (IOException e) { // TODO Auto-generated catch block
    e.printStackTrace(); }


  LatLng pos = new LatLng(latitude, longtitude);

    // Get a handle to the Map Fragment
    GoogleMap map = ((MapFragment) getFragmentManager()
            .findFragmentById(R.id.map)).getMap();

    map.setMyLocationEnabled(true);
    map.moveCamera(CameraUpdateFactory.newLatLngZoom(pos, 13));

    map.addMarker(new MarkerOptions()
            .title(adresa)
            .snippet("Ovde nešto napiši.")
            .position(pos));


}


}


谢谢!

最佳答案

问题是您要设置多个按钮,但是整个对象只有一个adresa。当你说

adresa = c.getString(2);


您将覆盖以前在adresa中的值。但是,问题在于设置了侦听器:

 public void onClick(View v) {
            // Perform action on click
            Intent activityChangeIntent = new Intent(DatabasesActivity.this, PrikazMape.class);
            activityChangeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            activityChangeIntent.putExtra("add", adresa);

            DatabasesActivity.this.startActivity(activityChangeIntent);
 }


设置时,不会将adresa的当前值复制到侦听器中。它只是说单击按钮时,要在onClick中运行代码;然后该代码将使用adresa当前具有的任何字符串,这将是循环中最后设置的字符串。

解决此问题的一种方法是定义自己的实现OnClickListener的类,而不是依赖于匿名类。然后,您可以添加一个构造函数,使您可以将地址存储在侦听器中。

private class OnClickListenerWithAdresa {
    private String mAdresa;
    public OnClickListenerWithAdresa(String adresa) {
        this.mAdresa = adresa;
    }
    public void onClick(View v) {
        // Perform action on click
        Intent activityChangeIntent = new Intent(DatabasesActivity.this, PrikazMape.class);
        activityChangeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        activityChangeIntent.putExtra("add", mAdresa); // NOTE use the listener's private field
        DatabasesActivity.this.startActivity(activityChangeIntent);
    }
}


然后在循环中设置监听器:

button.setOnClickListener(new OnClickListenerWithAdresa(adresa));


这将采用adresa的当前值,并将String引用复制到新的OnClickListenerWithAdresa。这将确保为每个按钮使用正确的adresa

我认为不太干净的另一种方法是在设置侦听器之前在循环内定义一个final变量:

        final String adresaForListener = adresa;

        button.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                // Perform action on click
                Intent activityChangeIntent = new Intent(DatabasesActivity.this, PrikazMape.class);
                activityChangeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                activityChangeIntent.putExtra("add", adresaForListener);

               DatabasesActivity.this.startActivity(activityChangeIntent);
            }
        });


之所以有效,是因为您在循环中声明了新的final变量,然后在匿名类中使用了该变量。最终结果是,每次创建新的侦听器时都会创建一个新的adresaForListener变量,因此每个侦听器都有自己的变量。这称为“关闭”。

10-08 02:24