标签内的网格布局

Question

我是Android新手,因此遇到了这样的问题.

如何更改布局:

至:

XML fragment_main:

<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: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="com.example.snbgearassistant.MainActivity$PlaceholderFragment" >


<TextView
    android:id="@+id/section_label"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

</RelativeLayout>

所以我需要这些标签具有不同内容的网格布局.

Answer 1

您必须在ViewPager中使用GridView.所以,在你的MainActivity,你会有这个布局.

创建activity_main.xml布局

这是主要布局.一切都将生活在其中,包括你的片段和标签.

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.myapp.gridview.MainActivity" />

创建MainActivity.java类

public class MainActivity extends ActionBarActivity implements ActionBar.TabListener 
{

    SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);

        // Here we load the xml layout we created above
        setContentView(R.layout.activity_main);

        // Set up the action bar.
        final ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        // When swiping between different sections, select the corresponding
        // tab. We can also use ActionBar.Tab#select() to do this if we have
        // a reference to the Tab.
        mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() 
        {
            @Override
            public void onPageSelected(int position) 
            {
                actionBar.setSelectedNavigationItem(position);
            }
        });

        // For each of the sections in the app, add a tab to the action bar.
        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) 
        {
            // Create a tab with text corresponding to the page title defined by
            // the adapter. Also specify this Activity object, which implements
            // the TabListener interface, as the callback (listener) for when
            // this tab is selected.
            actionBar.addTab(
                    actionBar.newTab()
                            .setText(mSectionsPagerAdapter.getPageTitle(i))
                            .setTabListener(this));
        }
    }


    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) 
    {
        // When the given tab is selected, switch to the corresponding page in
        // the ViewPager.
        mViewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) 
    {

    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) 
    {

    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter
    {

        public SectionsPagerAdapter(FragmentManager fm) 
        {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) 
        {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).
            return new PlaceholderFragment();
        }

        @Override
        public int getCount() 
        {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) 
        {
            Locale l = Locale.getDefault();
            switch (position) 
            {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);
                case 2:
                    return getString(R.string.title_section3).toUpperCase(l);
            }
            return null;
        }
    }
}

不要忘记R.string.title_section1, ...在代码上为这些字符串创建字符串,否则您将出错.

现在我们必须为片段创建一个布局(将在选项卡内显示的页面),它必须包含一个GridView.

创建fragment_main.xml布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <GridView
        android:id="@+id/gridview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:verticalSpacing="0dp"
        android:horizontalSpacing="0dp"
        android:stretchMode="columnWidth"
        android:numColumns="2" />
</FrameLayout>

现在让我们定义片段类,它将负责扩展此布局并处理视图.

创建一个片段来膨胀GridView布局:PlaceHolderFragment.java

/**
 * A placeholder fragment containing a the gridview
 */
public class PlaceholderFragment extends Fragment 
{
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);

        // Here we inflate the layout we created above
        GridView gridView = (GridView) rootView.findViewById(R.id.gridview);
        gridView.setAdapter(new MyAdapter(MainActivity.this.getApplicationContext()));

        return rootView;
    }
}

现在我们必须创建一个适配器类来处理每个项目GridView,这样你就可以管理每个项目的行为.

创建适配器以支持GridView项:MyAdapter.java

正如您在此处所看到的,我们将一些项添加到GridView中,方法是将它们添加到适配器类末尾定义ArrayList的类型Item中.

private class MyAdapter extends BaseAdapter
{
        private List<Item> items = new ArrayList<Item>();
        private LayoutInflater inflater;

        public MyAdapter(Context context)
        {
            inflater = LayoutInflater.from(context);

            items.add(new Item("Image 1", Color.GREEN));
            items.add(new Item("Image 2", Color.RED));
            items.add(new Item("Image 3", Color.BLUE));
            items.add(new Item("Image 4", Color.GRAY));
            items.add(new Item("Image 5", Color.YELLOW));
        }

        @Override
        public int getCount() {
            return items.size();
        }

        @Override
        public Object getItem(int i)
        {
            return items.get(i);
        }

        @Override
        public long getItemId(int i)
        {
            return items.get(i).colorId;
        }

        @Override
        public View getView(int i, View view, ViewGroup viewGroup)
        {
            View v = view;
            ImageView picture;
            TextView name;

            if(v == null)
            {
                v = inflater.inflate(R.layout.gridview_item, viewGroup, false);
                v.setTag(R.id.picture, v.findViewById(R.id.picture));
                v.setTag(R.id.text, v.findViewById(R.id.text));
            }

            picture = (ImageView)v.getTag(R.id.picture);
            name = (TextView)v.getTag(R.id.text);

            Item item = (Item)getItem(i);

            picture.setBackgroundColor(item.colorId);
            name.setText(item.name);

            return v;
        }

        private class Item
        {
            final String name;
            final int colorId;

            Item(String name, int drawableId)
            {
                this.name = name;
                this.colorId = drawableId;
            }
        }
    }

现在,为了使GridView项目保持正确的宽度,并排排列,我们使用自定义类来定义测量的尺寸.

为什么需要这样做？根据@ kcoppock的回答:

基本上,在Android的ImageView类中,除非您硬编码宽度和高度,否则无法简单地指定"嘿,保持此视图的正方形宽高比(宽度/高度)".您可以LayoutParams在适配器的getView中进行一些手动调整,但坦率地说,让ImageView处理所有测量更加简单,只需覆盖结果就可以说"无论宽度到底是什么,让我的高度保持不变".你永远不必考虑它,它总是方形的,它只是按预期工作.基本上这是保持视图方块的最简单方法.

创建一个SquareImageView.java类

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ImageView;

public class SquareImageView extends ImageView
{
    public SquareImageView(Context context)
    {
        super(context);
    }

    public SquareImageView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
    }

    public SquareImageView(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(getMeasuredWidth(), getMeasuredWidth()); //Snap to width
    }
}

现在我们必须为GridView项目定义XML布局.

创建XML布局gridview_item.xml

如您所见,这里我们在布局中添加两个项目.一个是类型的元素SquareImageView(我们在上面创建的类),TextView它是每个图像的标签.

<?xml version="1.0" encoding="utf-8"?>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <com.myapp.gridview.SquareImageView
        android:id="@+id/picture"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"
        />
    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="10dp"
        android:paddingRight="10dp"
        android:paddingTop="15dp"
        android:paddingBottom="15dp"
        android:layout_gravity="bottom"
        android:textColor="@android:color/white"
        android:background="#55000000"
        />
</FrameLayout>

在这里,我测试了代码,这是最终的结果.当然,您可以更改图像的颜色,但这是您应该遵循的方法.

注意:要设置的图像,而不是颜色的GridView项目,在你getView()的方法MyAdapter类使用setImageResource(int)代替setBackgroundColor(int).