Java 意图中的信息不会从一个活动发送到另一个活动
作为Android的新手,我正在开发一款Android应用程序,它可以将信息从一个活动传递到另一个活动。在第一个活动中以正确的方式检索信息-将其记录到日志cat-,但在第二个活动中未接收到该信息,因为通过intents传递的值返回null。这就是我被困的地方,任何提示或帮助都将不胜感激 第一个Java类:Java 意图中的信息不会从一个活动发送到另一个活动,java,android,android-intent,Java,Android,Android Intent,作为Android的新手,我正在开发一款Android应用程序,它可以将信息从一个活动传递到另一个活动。在第一个活动中以正确的方式检索信息-将其记录到日志cat-,但在第二个活动中未接收到该信息,因为通过intents传递的值返回null。这就是我被困的地方,任何提示或帮助都将不胜感激 第一个Java类: package de.die_web_agenten.www.runinstant; import android.app.Activity; import android.app.Aler
package de.die_web_agenten.www.runinstant;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.ActivityNotFoundException;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
import de.die_web_agenten.www.runinstant.db.TaskContract;
import de.die_web_agenten.www.runinstant.db.TaskDBHelper;
public class AndroidBarcodeQrExample extends Activity {
/** Called when the activity is first created. */
static final String ACTION_SCAN = "com.google.zxing.client.android.SCAN";
private ListAdapter listAdapter;
private TaskDBHelper helper;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_barcode);
}
public void scanBar(View v) {
try {
Intent intent = new Intent(ACTION_SCAN);
intent.putExtra("SCAN_MODE", "PRODUCT_MODE");
startActivityForResult(intent, 0);
} catch (ActivityNotFoundException anfe) {
showDialog(AndroidBarcodeQrExample.this, "No Scanner Found", "Download a scanner code activity?", "Yes", "No").show();
}
}
public void scanQR(View v) {
try {
Intent intent = new Intent(ACTION_SCAN);
intent.putExtra("SCAN_MODE", "QR_CODE_MODE");
startActivityForResult(intent, 0);
} catch (ActivityNotFoundException anfe) {
showDialog(AndroidBarcodeQrExample.this, "No Scanner Found", "Download a scanner code activity?", "Yes", "No").show();
}
}
private static AlertDialog showDialog(final Activity act, CharSequence title, CharSequence message, CharSequence buttonYes, CharSequence buttonNo) {
AlertDialog.Builder downloadDialog = new AlertDialog.Builder(act);
downloadDialog.setTitle(title);
downloadDialog.setMessage(message);
downloadDialog.setPositiveButton(buttonYes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialogInterface, int i) {
Uri uri = Uri.parse("market://search?q=pname:" + "com.google.zxing.client.android");
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
try {
act.startActivity(intent);
} catch (ActivityNotFoundException anfe) {
}
}
});
downloadDialog.setNegativeButton(buttonNo, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialogInterface, int i) {
}
});
return downloadDialog.show();
}
private void updateUI() {
helper = new TaskDBHelper(AndroidBarcodeQrExample.this);
SQLiteDatabase sqlDB = helper.getReadableDatabase();
Cursor cursor = sqlDB.query(TaskContract.TABLE,
new String[]{ TaskContract.Columns.SCAN_RESULT, TaskContract.Columns.SCAN_FORMAT,TaskContract.Columns._id,
TaskContract.Columns.DATE},
null, null, null, null, null
);
listAdapter = new SimpleCursorAdapter(
this,
R.layout.task_view,
cursor,
new String[]{TaskContract.Columns.SCAN_FORMAT, TaskContract.Columns.SCAN_RESULT, TaskContract.Columns._id},
new int[]{R.id.taskTextView},
0
);
this.setListAdapter(listAdapter);
}
public void onActivityResult(int requestCode, int resultCode, Intent intent) {
if (requestCode == 0) {
if (resultCode == RESULT_OK) {
String contents = intent.getStringExtra("SCAN_RESULT");
String format = intent.getStringExtra("SCAN_RESULT_FORMAT");
Toast toast = Toast.makeText(this, "Content:" + contents + " Format:" + format, Toast.LENGTH_LONG);
toast.show();
/*Intent SecondIntent = new Intent(AndroidBarcodeQrExample.this, SecondListActivity.class);
SecondIntent.putExtra("SCAN_RESULT", contents);
startActivity(SecondIntent);*/
Intent SecondIntent = new Intent(getBaseContext(), SecondListActivity.class);
intent.putExtra("SCAN_RESULT", contents);
intent.putExtra("SCAN_RESULT_FORMAT", format);
startActivity(SecondIntent);
Log.d("ADebugTag", "Value: " + (contents));
Log.d("BDebugTag", "Value: " + (format));
//updateUI();
//Context context = getApplicationContext();
//CharSequence text = "Informationen erfolgreich gespeichert!";
//int duration = Toast.LENGTH_SHORT;
//Toast toast = Toast.makeText(context, text, duration);
}
}
}
public void setListAdapter(ListAdapter listAdapter) {
this.listAdapter = listAdapter;
}
}
这是第二项活动,未以正确的方式检索信息:
package de.die_web_agenten.www.runinstant;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.SimpleCursorAdapter;
import java.util.ArrayList;
import de.die_web_agenten.www.runinstant.db.TaskContract;
import de.die_web_agenten.www.runinstant.db.TaskDBHelper;
public class SecondListActivity extends ListActivity {
// declare class variables
private ArrayList<Item> m_parts = new ArrayList<Item>();
private Runnable viewParts;
private ItemAdapter m_adapter;
private ListAdapter listAdapter;
private TaskDBHelper helper;
/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// instantiate our ItemAdapter class
m_adapter = new ItemAdapter(this, R.layout.list_item, m_parts);
setListAdapter(m_adapter);
// here we are defining our runnable thread.
viewParts = new Runnable(){
public void run(){
handler.sendEmptyMessage(0);
}
};
// here we call the thread we just defined - it is sent to the handler below.
Thread thread = new Thread(null, viewParts, "MagentoBackground");
thread.start();
}
private void updateUI() {
helper = new TaskDBHelper(SecondListActivity.this);
SQLiteDatabase sqlDB = helper.getReadableDatabase();
Cursor cursor = sqlDB.query(TaskContract.TABLE,
new String[]{TaskContract.Columns.SCAN_RESULT, TaskContract.Columns.SCAN_FORMAT,
TaskContract.Columns.DATE, TaskContract.Columns._id },
null, null, null, null, null
);
listAdapter = new SimpleCursorAdapter(
this,
R.layout.task_view,
cursor,
new String[]{TaskContract.Columns.SCAN_FORMAT, TaskContract.Columns.SCAN_RESULT, TaskContract.Columns._id},
new int[]{R.id.taskTextView},
0
);
this.setListAdapter(listAdapter);
}
private Handler handler = new Handler()
{
public void handleMessage(Message msg)
{
// create some objects
// here is where you could also request data from a server
// and then create objects from that data.
/*String sql = String.format("DELETE FROM %s WHERE %s = '%s'",
TaskContract.TABLE,
TaskContract.Columns.SCAN_FORMAT,
TaskContract.Columns.SCAN_RESULT
);
helper = new TaskDBHelper(SecondListActivity.this);
SQLiteDatabase sqlDB = helper.getWritableDatabase();
sqlDB.execSQL(sql);*/
Intent SecondIntent = getIntent();
String contents = SecondIntent.getStringExtra("SCAN_RESULT");
//String contents = SecondIntent.getStringExtra("SCAN_RESULT", contents);
String format = SecondIntent.getStringExtra("SCAN_RESULT_FORMAT");
m_parts.add(new Item(contents, format, 0));
m_parts.add(new Item("MyItemName #2", "This is item #2", 0));
Log.d("CDebugTag", "Value: " + (contents));
//Log.d("DDebugTag", "Value: " + (format));
/*m_parts.add(new Item("MyItemName", "This is item #3", 0));
m_parts.add(new Item("MyItemName #2", "This is item #4", 0));
m_parts.add(new Item("MyItemName", "This is item #5", 0));
m_parts.add(new Item("MyItemName #2", "This is item #6", 0));
m_parts.add(new Item("MyItemName", "This is item #7", 0));
m_parts.add(new Item("MyItemName #2", "This is item #8", 0));
m_parts.add(new Item("MyItemName", "This is item #9", 0));
m_parts.add(new Item("MyItemName #2", "This is item #10", 0));*/
m_adapter = new ItemAdapter(SecondListActivity.this, R.layout.list_item, m_parts);
// display the list.
setListAdapter(m_adapter);
//updateUI();
}
};
}
package de.die\u web\u agenten.www.runinstant;
导入android.app.ListActivity;
导入android.content.Intent;
导入android.database.Cursor;
导入android.database.sqlite.SQLiteDatabase;
导入android.os.Bundle;
导入android.os.Handler;
导入android.os.Message;
导入android.util.Log;
导入android.widget.ListAdapter;
导入android.widget.SimpleCursorAdapter;
导入java.util.ArrayList;
导入de.die_web_agenten.www.runinstant.db.TaskContract;
导入de.die_web_agenten.www.runinstant.db.TaskDBHelper;
公共类SecondListActivity扩展了ListActivity{
//声明类变量
private ArrayList m_parts=new ArrayList();
私有可运行视图部件;
专用项目适配器m_适配器;
私有ListAdapter ListAdapter;
私人任务助手;
/**在首次创建活动时调用*/
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//实例化我们的ItemAdapter类
m_adapter=新项目适配器(此,R.layout.list_项目,m_零件);
setListAdapter(m_适配器);
//这里我们定义了可运行线程。
viewParts=新的可运行(){
公开募捐{
handler.sendEmptyMessage(0);
}
};
//这里我们调用刚刚定义的线程——它被发送到下面的处理程序。
线程线程=新线程(空,viewParts,“MagentoBackground”);
thread.start();
}
私有void updateUI(){
helper=新TaskDBHelper(SecondListActivity.this);
SQLiteDatabase sqlDB=helper.getReadableDatabase();
Cursor Cursor=sqlDB.query(TaskContract.TABLE,
新字符串[]{TaskContract.Columns.SCAN_结果,TaskContract.Columns.SCAN_格式,
TaskContract.Columns.DATE,TaskContract.Columns.\u id},
空,空,空,空,空,空
);
listAdapter=新的SimpleCorsorAdapter(
这
R.layout.task_视图,
光标,
新字符串[]{TaskContract.Columns.SCAN_格式,TaskContract.Columns.SCAN_结果,TaskContract.Columns.\u id},
新建int[]{R.id.taskTextView},
0
);
这个.setListAdapter(listAdapter);
}
私有处理程序=新处理程序()
{
公共无效handleMessage(消息消息消息)
{
//创建一些对象
//在这里,您还可以从服务器请求数据
//然后根据该数据创建对象。
/*String sql=String.format(“从%s中删除,其中%s='%s'”,
TaskContract.TABLE,
TaskContract.Columns.SCAN_格式,
TaskContract.Columns.SCAN\u结果
);
helper=新TaskDBHelper(SecondListActivity.this);
SQLiteDatabase sqlDB=helper.getWritableDatabase();
execSQL(sql)*/
Intent SecondIntent=getIntent();
字符串内容=SecondIntent.getStringExtra(“扫描结果”);
//String contents=SecondIntent.getStringExtra(“扫描结果”,contents);
字符串格式=SecondIntent.getStringExtra(“扫描结果格式”);
m_parts.add(新项(内容、格式、0));
m#u parts.add(新项目(“MyItemName#2”,“这是项目#2”,0));
Log.d(“CDebugTag”,“Value:+(contents));
//d(“DDebugTag”,“值:”+(格式));
/*添加(新项目(“MyItemName”,“这是项目3”,0));
m#u parts.add(新项目(“MyItemName#2”,“这是项目#4”,0));
添加(新项目(“MyItemName”,“这是项目5”,0));
m#u parts.add(新项目(“MyItemName#2”,“这是项目#6”,0));
添加(新项目(“MyItemName”,“这是项目7”,0));
m#u parts.add(新项目(“MyItemName#2”,“这是项目#8”,0));
添加(新项目(“MyItemName”,“这是项目9”,0));
m#u parts.add(新项目(“MyItemName#2”,“这是项目#10”,0))*/
m_adapter=新项目适配器(SecondListActivity.this,R.layout.list_项目,m_部件);
//显示列表。
setListAdapter(m_适配器);
//updateUI();
}
};
}
这两个活动都已在应用程序的Android清单中注册:
<activity
android:name=".MapsActivity"
android:label="@string/title_activity_maps" />
<activity
android:name=".ResultsActivity"
android:label="@string/title_activity_results"
android:theme="@style/AppTheme.NoActionBar" />
<activity
android:name=".TrainingActivity"
android:label="@string/title_activity_training"
android:theme="@style/AppTheme.NoActionBar" />
<activity
android:name=".SecondListActivity"
android:label="@string/title_activity_list"
android:theme="@style/AppTheme.NoActionBar" />
<activity
android:name=".AndroidBarcodeQrExample"
android:label="@string/title_barcode_class"
android:theme="@style/AppTheme.NoActionBar" />
我被困在这里,因为我不明白为什么在第二个活动中没有通过意图检索信息,因为Android应该发送意图,我在日志中没有收到任何错误。欢迎提供任何提示或信息,谢谢 处理程序对象需要回调参数
Handler handler = new Handler(new Handler.Callback() {
@Override
public boolean handleMessage(Message message) {
smth();
...
return messageHandled;
}
});
您可以通过使用Handler.Callback接口或实现您自己的子类来实现这一点,这比第一个选项更难,因此我建议使用上述实现。我试过了,确实是这样的
编辑1:返回消息是否已处理,以确保处理程序不会多次处理该消息。处理程序对象需要回调参数
Handler handler = new Handler(new Handler.Callback() {
@Override
public boolean handleMessage(Message message) {
smth();
...
return messageHandled;
}
});
您可以通过使用Handler.Callback接口或实现您自己的子类来实现这一点,这比第一个选项更难,因此我建议使用上述实现。我试过了,确实是这样的
编辑1:返回mes