创建多级列表视图应用程序

Question

所以这是代码。它非常自我解释。我遇到的唯一问题是保留int级别的值。它每次都丢失了。我需要保留这个值，它会起作用。这是一个快照。它应该可以扩展到每个级别的深度和多个项目。

XML代码：

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

<ListView
    android:id="@+id/listView1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true" >
</ListView>

</RelativeLayout>

Java代码：

package com.example.kjkjsdkjdsjkdfs;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends ListActivity {
String categoryselected = "main";
public int level = 0;

@SuppressWarnings("null")
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String[] array;
    Intent received = getIntent();
    // Setup as main ListView
    if (received == null || !received.hasExtra("array")) {
        array = new String[] { "1", "2", "3" };
    }

    // Setup as sub ListView
    else {
        array = received.getStringArrayExtra("array");

    }
    if(received != null || !received.hasExtra("level")) {
        level = received.getIntExtra("level", 0);
    }
    setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, array));
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    level = level + 1;
    Intent starting = new Intent(MainActivity.this, MainActivity.class);
    switch (level) {
    case 1:
        switch (position) {
        case 0:
            starting.putExtra("array", new String[] { "1a", "1b", "1c" });
            starting.putExtra("level", level);
            break;
        case 1:
            starting.putExtra("array", new String[] { "2a", "2b", "2c" });
            starting.putExtra("level", level);
            break;
        case 2:
            starting.putExtra("array", new String[] { "3a", "3b", "3c" });
            starting.putExtra("level", level);
            break;
        }

        break;

    case 2:
        switch (position) {
        case 0:
            starting.putExtra("array", new String[] { "1aa", "1ab" });
            starting.putExtra("level", level);
            break;

        }

        break;
    case 3:
        switch (position) {
        case 0:
            starting.putExtra("array", new String[] { "1aaa", "1aab" });
            starting.putExtra("level", level);
            break;
        }
        break;
    }

    startActivity(starting);

}

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

}

Answer 1

更新您的代码如下：

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class ListItems extends ListActivity {
    String categoryselected = "main";
    public int level = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        String[] array;
        Intent received = getIntent();
        // Setup as main ListView
        if (received == null || !received.hasExtra("array")) {
            array = new String[] { "1", "2", "3" };
        }

        // Setup as sub ListView
        else {
            array = received.getStringArrayExtra("array");

        }
        if(received != null || !received.hasExtra("level")) {
            level = received.getIntExtra("level", 0);
        }
        setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, array));
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        level = level + 1;
        Intent starting = new Intent(ListItems.this, ListItems.class);
        switch (level) {
        case 1:
            switch (position) {
            case 0:
                starting.putExtra("array", new String[] { "1a", "1b", "1c" });
                starting.putExtra("level", level);
                break;
            case 1:
                starting.putExtra("array", new String[] { "2a", "2b", "2c" });
                starting.putExtra("level", level);
                break;
            case 2:
                starting.putExtra("array", new String[] { "3a", "3b", "3c" });
                starting.putExtra("level", level);
                break;
            }

            break;

        case 2:
            switch (position) {
            case 0:
                starting.putExtra("array", new String[] { "1aa", "1ab" });
                starting.putExtra("level", level);
                break;

            }

            break;
        case 3:
            switch (position) {
            case 0:
                starting.putExtra("array", new String[] { "1aaa", "1aab" });
                starting.putExtra("level", level);
                break;
            }
            break;
        }

        startActivity(starting);

    }

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

}