Clover launcher

<intent-filter>
</intent-filter>

中添加

<category android:name="android.intent.category.HOME" />
 <category android:name="android.intent.category.DEFAULT" />

作用
把应用程序作为home

知识点：GridView 显示数据表格（一种控件） 宫格布局

GridView属性说明
android:columnWidth 设置列的宽度
android:horizontalSpacing两列之间的间距
android:verticalSpacing两行之间的间距
android:numColumns设置列数。取值有2种。
(01)可以设置为数字，比如：”2”表示有两列。
(02)可以设置为“auto_fit”，表示根据“屏幕宽
度”和“GridView宽度”来动态匹配。
渲染问题解决办法：在项目项目中找到\ app \ src \ main \ res \ values \ styles.xml文件，把下面这一栏

<style name =“AppTheme”parent =“Theme.AppCompat.Light.DarkActionBar”> 

改为

<style name =“AppTheme”parent =“Base.Theme.AppCompat.Light.DarkActionBar”> 

https://blog.csdn.net/dafei93/article/details/80471615

activity_main.xml
加入宫格布局 GridView

<GridView
        android:id="@+id/apps_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="180dp"
        android:numColumns="4"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

MainActivity.java

package com.example.administrator.cloverlauncher;

import java.util.List;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.pm.ResolveInfo;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class MainActivity extends Activity {
    private List<ResolveInfo> mApps;
    private GridView mGrid;

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

        loadApps();
        setContentView(R.layout.activity_main);
        mGrid = (GridView) findViewById(R.id.apps_list);
        mGrid.setAdapter(new AppsAdapter());

        mGrid.setOnItemClickListener(listener);
    }

    private OnItemClickListener listener = new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,long id) {
            ResolveInfo info = mApps.get(position);

            //该应用的包名
            String pkg = info.activityInfo.packageName;
            //应用的主activity类
            String cls = info.activityInfo.name;

            ComponentName componet = new ComponentName(pkg, cls);

            Intent i = new Intent();
            i.setComponent(componet);
            startActivity(i);
        }

    };


    private void loadApps() {
        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);

        mApps = getPackageManager().queryIntentActivities(mainIntent, 0);
    }



    public class AppsAdapter extends BaseAdapter {
        public AppsAdapter() {
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView i;


            if (convertView == null) {
                i = new ImageView(MainActivity.this);
                i.setScaleType(ImageView.ScaleType.FIT_CENTER);
                i.setLayoutParams(new GridView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
            } else {
                i = (ImageView) convertView;
            }

            ResolveInfo info = mApps.get(position);
            i.setImageDrawable(info.activityInfo.loadIcon(getPackageManager()));

            return i;
        }

        public final int getCount() {
            return mApps.size();
        }

        public final Object getItem(int position) {
            return mApps.get(position);
        }

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

}