关于Launcher

Launcher是安卓系统中的桌面启动器，安卓系统的桌面UI统称为Launcher。
Launcher是安卓系统中的主要程序组件之一，安卓系统中如果没有Launcher就无法启动安卓桌面。
那么你如果想要自定义一个安卓桌面，那么就需要修改调整这部分内容。

Launcher上手

下面我就通过一个简单的UI(UI源码）界面来演示怎么自定义Launcher Activity—-自定义桌面。

新建项目

Android Studio新建一个安卓项目。

选择Empty Activity，然后Next。

然后Finish完成项目创建。等初始化完成，项目结构如下：

修改Manifest

在MainActivity的intent-filter标签内添加下边两行代码：

1 2	<category android:name="android.intent.category.HOME" /> <category android:name="android.intent.category.DEFAULT" />

修改activity_main.xml

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <GridView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/apps_list"
        android:numColumns="4" />


</androidx.constraintlayout.widget.ConstraintLayout>

新建ColorBaseAdapter.kt

package mobi.huanyuan.testlauncher

import android.annotation.SuppressLint
import android.app.Activity
import android.content.Context
import android.graphics.Color
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.BaseAdapter
import android.widget.TextView
import android.widget.Toast
import androidx.cardview.widget.CardView


class ColorBaseAdapter : BaseAdapter (){
    private val list = colors()

    @SuppressLint("ViewHolder", "InflateParams")
    override fun getView(position:Int, convertView: View?, parent: ViewGroup?):View{
        // Inflate the custom view
        val inflater = parent?.context?.
        getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        val view = inflater.inflate(R.layout.custom_view,null)

        // Get the custom view widgets reference
        val tv = view.findViewById<TextView>(R.id.tv_name)
        val card = view.findViewById<CardView>(R.id.card_view)

        // Display color name on text view
        tv.text = list[position].first

        // Set background color for card view
        card.setCardBackgroundColor(list[position].second)

        // Set a click listener for card view
        card.setOnClickListener{
            // Show selected color in a toast message
            Toast.makeText(parent.context,
                "Clicked : ${list[position].first}",Toast.LENGTH_SHORT).show()

            // Get the activity reference from parent
            val activity  = parent.context as Activity

            // Get the activity root view
            val viewGroup = activity.findViewById<ViewGroup>(android.R.id.content)
                .getChildAt(0)

            // Change the root layout background color
            viewGroup.setBackgroundColor(list[position].second)
        }

        // Finally, return the view
        return view
    }

    override fun getItem(position: Int): Any? {
        return list[position]
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getCount(): Int {
        return list.size
    }

    private fun colors():List<Pair<String,Int>>{
        return listOf(
            Pair("INDIANRED",Color.parseColor("#CD5C5C")),
            Pair("LIGHTCORAL",Color.parseColor("#F08080")),
            Pair("SALMON",Color.parseColor("#FA8072")),
            Pair("DARKSALMON",Color.parseColor("#E9967A")),
            Pair("LIGHTSALMON",Color.parseColor("#FFA07A")),
            Pair("CRIMSON",Color.parseColor("#DC143C")),
            Pair("RED",Color.parseColor("#FF0000")),
            Pair("FIREBRICK",Color.parseColor("#B22222")),
            Pair("DARKRED",Color.parseColor("#8B0000")),

            Pair("PINK",Color.parseColor("#FFC0CB")),
            Pair("LIGHTPINK",Color.parseColor("#FFB6C1")),
            Pair("HOTPINK",Color.parseColor("#FF69B4")),
            Pair("DEEPPINK",Color.parseColor("#FF1493")),
            Pair("MEDIUMVIOLETRED",Color.parseColor("#C71585")),
            Pair("PALEVIOLETRED",Color.parseColor("#DB7093"))
        )
    }
}

新建custom_view.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/card_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardCornerRadius="5dp"
    app:cardElevation="5dp"
    app:cardMaxElevation="7dp"
    app:contentPadding="20dp"
    android:layout_margin="5dp" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:layout_editor_absoluteX="0dp"
        tools:layout_editor_absoluteY="0dp">
        <TextView
            android:id="@+id/tv_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textStyle="bold"
            android:layout_gravity="center" />
    </LinearLayout>

</androidx.cardview.widget.CardView>

修改MainActivity.kt

package mobi.huanyuan.testlauncher

import android.os.Bundle
import android.widget.GridView
import androidx.appcompat.app.AppCompatActivity
import mobi.huanyuan.testlauncher.databinding.ActivityMainBinding


class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // Get an instance of base adapter
        val adapter = ColorBaseAdapter()

        // Set the grid view adapter
        binding.appsList.adapter = adapter

        // Configure the grid view
        binding.appsList.numColumns = 2
        binding.appsList.horizontalSpacing = 15
        binding.appsList.verticalSpacing = 15
        binding.appsList.stretchMode = GridView.STRETCH_COLUMN_WIDTH
    }

}