我是 android 的新手,我有一个问题。我想在单击按钮时将变量“adresa”从 for(或 while)循环发送到另一个 Activity ,但总是从循环发送最后一个值。 这是代码: 附言。对不起我的英语不好 这是第一个 Activity
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();
}
}
第二个
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
问题是您正在设置多个按钮,但整个对象只有一个 adresa
。当你说
adresa = c.getString(2);
您将覆盖以前在 adresa
中的值。但是,问题在于设置监听器:
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);
}
不在设置时将 adresa
的当前值复制到监听器中。它只是说当按钮被点击时,运行onClick
中的代码;并且该代码将使用 adresa
当前拥有的任何字符串,这将是循环中最后设置的任何字符串。
解决此问题的一种方法是定义您自己的实现 OnClickListener
的类,而不是依赖匿名类。然后您可以添加一个构造函数,让您将地址存储在监听器中。
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,在你的循环中,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
。
另一种方法,我认为不太干净,是在设置监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);
}
});
这是有效的,因为您在循环内部声明了新的final
变量,然后在匿名类中使用它;最终结果将是每次创建新的监听器时都会创建一个新的 adresaForListener
变量,因此每个监听器都有自己的变量。它被称为“关闭”。
关于java - 如何将变量从 for(或 while)循环发送到另一个 Activity ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24071345/