Android组件学习笔记（自定义设计View，以及布局直接引入的快捷方式）

跟着一本书的教程做的一个简单的跟着手指移动的小球demo，记录一下笔记

自定义View之后引入使用

自定义View的代码（简单来说就是新建一个继承View的类重写一些函数，写出你想要的东西）：

package com.example.hp.planemove;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;/** * Created by HP on 2017/11/9. */public class DrawView extends View {    public float currentX=40;    public float currentY=50;    Paint p=new Paint();    public DrawView(Context context)    {        super(context);    }    public DrawView(Context context, AttributeSet set)    {        super(context,set);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        p.setColor(Color.RED);        canvas.drawCircle(currentX,currentY,55,p);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        currentX=event.getX();        currentY=event.getY();        invalidate();        return true;    }}

布局代码：

<?xml version="1.0" encoding="utf-8"?><android.support.constraint.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="com.example.hp.planemove.MainActivity">    <LinearLayout        android:id="@+id/root"        android:layout_width="368dp"        android:layout_height="495dp"        android:orientation="vertical"        tools:layout_editor_absoluteX="8dp"        tools:layout_editor_absoluteY="8dp"></LinearLayout></android.support.constraint.ConstraintLayout>

mainactivity代码：

package com.example.hp.planemove;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.LinearLayoutCompat;import android.util.DisplayMetrics;import android.view.Display;import android.view.KeyEvent;import android.view.View;import android.view.Window;import android.view.WindowManager;import android.widget.Button;import android.widget.LinearLayout;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        LinearLayout root=(LinearLayout)findViewById(R.id.root);       final DrawView drawView=new DrawView(this);        drawView.setMinimumHeight(500);        drawView.setMinimumWidth(300);        root.addView(drawView);    }}

第二种方法直接在布局界面引入自定义组件

布局代码如下：

<?xml version="1.0" encoding="utf-8"?><android.support.constraint.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="com.example.hp.planemove.MainActivity">    <LinearLayout        android:id="@+id/root"        android:layout_width="368dp"        android:layout_height="495dp"        android:orientation="vertical"        tools:layout_editor_absoluteX="8dp"        tools:layout_editor_absoluteY="8dp"></LinearLayout>    <com.example.hp.planemove.DrawView        android:layout_width="match_parent"        android:layout_height="match_parent" /></android.support.constraint.ConstraintLayout>

mainactivity代码就保持最初新建项目时就好了，不需要再写了。