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我试图为 ArrayList 为 android 应用程序设计一个自定义数组适配器。

我需要的是要显示的项目列表，其中每个项目由一个复选框和一个描述性文本组成。我想我需要实现 baseAdapter 的扩展来做到这一点。我无法让它工作。请指出我的错误。

以下是我的主要活动屏幕，仅由一个按钮和一个 listView 组成，两者都已打包在一个 RelativeLayout 中。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/background"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".HomeActivity" >

    <Button
        android:id="@+id/addTaskButton"
        android:textSize="30sp"
        style="@style/bottomButton"
        android:text="@string/addTaskButtonText"/>

    <ListView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@id/addTaskButton"    
        android:id="@+id/list">     
    </ListView>



</RelativeLayout>

以下是上述屏幕的 listView 中单个项目的布局。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/singleItemContainer" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip">
    <CheckBox
        android:id="@+id/taskDoneCheckBox"
        android:layout_alignParentLeft="true">      
    </CheckBox>
    <TextView 
        android:id="@+id/taskDescriptionTextView"
        android:layout_toRightOf="@+id/taskDoneCheckBox"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:padding="10dip"/>
</RelativeLayout>

以下是我创建的自定义适配器。

public class MyListAdapter extends BaseAdapter {

    private Activity activity;
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater=null;


    public MyListAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data=d;
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    }

    public int getCount() {
        return data.size();
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        if(convertView==null)
            vi = inflater.inflate(R.layout.list_item, null);

        CheckBox taskDoneCheckBox = (CheckBox) vi.findViewById(R.id.taskDoneCheckBox);
        TextView taskDescriptionTextView = (TextView)vi.findViewById(R.id.taskDescriptionTextView); 

        HashMap<String, String> task = new HashMap<String, String>();
        task = data.get(position);

        // Setting all values in listview
        if(task.get(HomeActivity.IS_TASK_DONE) == "false")
            taskDoneCheckBox.setChecked(false);
        else
            taskDoneCheckBox.setChecked(true);

        taskDescriptionTextView.setText(task.get(HomeActivity.TASK_DESCRIPTION));
        return vi;
    }
}

最后是 mainActivity 类。我已经标记了它的存在使应用程序崩溃的行。

public class HomeActivity extends Activity {

    public static final String IS_TASK_DONE = "isTaskDone";
    public static final String TASK_DESCRIPTION = "taskDescription";

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

        //setting up font for the "add task" button.
        Typeface tf = Typeface.createFromAsset(getAssets(),"Fonts/doridrobot.ttf");
        Button addTaskButton = (Button) findViewById(R.id.addTaskButton);
        addTaskButton.setTypeface(tf);

        // storing string resources into HashMap
        ArrayList<HashMap<String,String>> taskList = new ArrayList<HashMap<String,String>>();

        HashMap<String,String> task = new HashMap<String,String>();
        task.put(IS_TASK_DONE, "false");
        task.put(TASK_DESCRIPTION, "Let this be task 1");
        taskList.add(task);

        HashMap<String,String> task1 = new HashMap<String,String>();
        task1.put(IS_TASK_DONE, "true");
        task1.put(TASK_DESCRIPTION, "Let this be task 2");
        taskList.add(task1);


        ListView itemList = (ListView) findViewById(R.id.list);
        adapter = new MyListAdapter(this,taskList);
        itemList.setAdapter(adapter);   //<----- THIS IS THE ONE

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.home, menu);
        return true;
    }

}

删除 OnCreate 函数中的最后一行“有助于”应用程序不会崩溃，但列表仍然为空......我该如何解决这个问题？

4

3 回答 3

0

请发布您的 logcat 输出以了解您到底在哪里崩溃，尽管我现在可以指出的一个错误是，

 public Object getItem(int position) {
    return position;
}

在这里你需要放

 public Object getItem(int position) {
    return data.get(position);
}
于 2013-08-18T12:30:30.543 回答
0

发布您的日志猫错误可能是因为您没有指定任何布局宽度和高度属性 android:layout_width="wrap_content" android:layout_height="wrap_content"

为 list_item 指定一些宽度和高度：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/singleItemContainer"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="10dip" >

<CheckBox
    android:id="@+id/taskDoneCheckBox"
    android:layout_alignParentLeft="true" 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
</CheckBox>

<TextView
    android:id="@+id/taskDescriptionTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:layout_toRightOf="@+id/taskDoneCheckBox" />

于 2013-08-18T12:37:53.200 回答
0

我已经检查过了，它正在工作：

litsitem.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <CheckBox
        android:id="@+id/taskDoneCheckBox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="" />

    <TextView
        android:id="@+id/taskDescriptionTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/checkBox1"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="Large Text"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <Button
        android:id="@+id/addTaskButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:text="Button" />

    <ListView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/addTaskButton" >
    </ListView>

</RelativeLayout>

HomeActivity.java

import java.util.ArrayList;
import android.os.*;
import android.widget.*;
import java.util.HashMap;
import android.app.Activity;

public class HomeActivity extends Activity {

    public static final String IS_TASK_DONE = "isTaskDone";
    public static final String TASK_DESCRIPTION = "taskDescription";

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

        ArrayList<HashMap<String,String>> taskList = new ArrayList<HashMap<String,String>>();

        HashMap<String,String> task = new HashMap<String,String>();
        task.put(IS_TASK_DONE, "false");
        task.put(TASK_DESCRIPTION, "Let this be task 1");
        taskList.add(task);

        HashMap<String,String> task1 = new HashMap<String,String>();
        task1.put(IS_TASK_DONE, "true");
        task1.put(TASK_DESCRIPTION, "Let this be task 2");
        taskList.add(task1);


        ListView itemList = (ListView) findViewById(R.id.list);
        adapter = new MyListAdapter(this, taskList);
        itemList.setAdapter(adapter);

    }
}

我的列表适配器

import java.util.ArrayList;
import java.util.HashMap;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.CheckBox;
import android.widget.TextView;

public class MyListAdapter extends BaseAdapter {

    private Context activity;
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater=null;


    public MyListAdapter(Context a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data=d;
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    }

    public int getCount() {
        return data.size();
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        if(convertView==null)
            vi = inflater.inflate(R.layout.listitem, null);

        CheckBox taskDoneCheckBox = (CheckBox) vi.findViewById(R.id.taskDoneCheckBox);
        TextView taskDescriptionTextView = (TextView)vi.findViewById(R.id.taskDescriptionTextView); 

        HashMap<String, String> task = new HashMap<String, String>();
        task = data.get(position);

        // Setting all values in listview
        if(task.get(HomeActivity.IS_TASK_DONE) == "false")
            taskDoneCheckBox.setChecked(false);
        else
            taskDoneCheckBox.setChecked(true);

        taskDescriptionTextView.setText(task.get(HomeActivity.TASK_DESCRIPTION));
        return vi;
    }
}
于 2013-08-18T13:00:18.903 回答