1.自定义view入门
1.继承自view
系统提供的view 如 TextView 、ImageView 都是继承自view的；
2.自定义一个TextView
通过自定义一个TextView 来熟悉继承自view 的自定义view的api用法
3.onMeasure
用来处理控件的大小
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
}
//获取宽高的模式 int widthMode = MeasureSpec.getMode(widthMeasureSpec); int heightMode = MeasureSpec.getMode(heightMeasureSpec); //mode //MeasureSpec.AT_MOST 指定了wrap_content //MeasureSpec.EXACTLY 指定了确切的值 match_parent fill_parent //MeasureSpec.UNSPECIFIED 尽可能的大
4.onDraw
用于绘制
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// canvas.drawText();
}
5.onTouchEvent
用于处理用户触摸事件
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_MOVE:
break;
case MotionEvent.ACTION_UP:
break;
}
return super.onTouchEvent(event);
}
6.自定义属性
用来配置自定义控件的属性
<?xml version="1.0" encoding="utf-8"?>
<resources>
<!-- 自定义控件的名称 name="TextView"-->
<declare-styleable name="TextView">
<attr name="text" format="string" />
<attr name="textColor" format="color" />
<attr name="textSize" format="dimension" />
<attr name="maxLength" format="integer" />
<attr name="background" format="reference|color" />
<!--枚举-->
<attr name="inputType" format="enum">
<enum name="number" value="1" />
<enum name="text" value="2" />
<enum name="password" value="3" />
</attr>
</declare-styleable>
</resources>
在布局中使用
<com.nb.customview.TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:text="张三"
app:textColor="@color/purple_500"
app:textSize="16" />
在自定义控件中获取
public TextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.TextView);
mText = typedArray.getString(R.styleable.TextView_text);
mTextSize = typedArray.getDimensionPixelSize(R.styleable.TextView_textSize, mTextSize);
mTextColor = typedArray.getColor(R.styleable.TextView_textColor, mTextColor);
typedArray.recycle();
}
7.完整的代码
package com.nb.customview;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import androidx.annotation.Nullable;
/**
* Created by DongKing on 2020/11/5
* Version 1.0
* Describe:自定义TextView
*/
class TextView extends View {
private static final String TAG = "TextView";
private String mText;
private int mTextSize = 15;
private int mTextColor = Color.BLACK;
private Paint mPaint;
// 在java 代码中new 的时候使用
public TextView(Context context) {
this(context, null);
}
// 在layout 中使用
public TextView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
//有style时使用
public TextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
//获取xml中设置的属性
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.TextView);
mText = typedArray.getString(R.styleable.TextView_nbText);
mTextSize = typedArray.getDimensionPixelSize(R.styleable.TextView_nbTextSize, sp2px(mTextSize));
mTextColor = typedArray.getColor(R.styleable.TextView_nbTextColor, mTextColor);
typedArray.recycle();
//初始化画笔
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setTextSize(mTextSize);
mPaint.setColor(mTextColor);
}
private int sp2px(int sp) {
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp,
getResources().getDisplayMetrics());
}
/**
* 指定宽高
* 针对不同的情况
*
* @param widthMeasureSpec
* @param heightMeasureSpec
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
//1.如果指定大小
int width = MeasureSpec.getSize(widthMeasureSpec);
//2.wrap_content 计算获取值
if (widthMode == MeasureSpec.AT_MOST) {
Rect bounds = new Rect();
mPaint.getTextBounds(mText, 0, mText.length(), bounds);
width = bounds.width() + getPaddingLeft() + getPaddingRight();
}
int height = MeasureSpec.getSize(heightMeasureSpec);
if (heightMode == MeasureSpec.AT_MOST) {
Rect bounds = new Rect();
mPaint.getTextBounds(mText, 0, mText.length(), bounds);
height = bounds.height() + getPaddingTop() + getPaddingBottom();
}
//设置控件的宽高
setMeasuredDimension(width, height);
}
/**
* 用于绘制
*
* @param canvas
*/
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint.FontMetricsInt fontMetrics = mPaint.getFontMetricsInt();
int dy = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
int baseLine = getHeight() / 2 + dy;
canvas.drawText(mText, getPaddingLeft(), baseLine, mPaint);
}
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:orientation="vertical"
tools:context=".MainActivity">
<LinearLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<com.nb.customview.TextView
android:padding="10dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@color/purple_200"
app:nbText="张三"
app:nbTextColor="@color/teal_200"
app:nbTextSize="20sp" />
</LinearLayout>
</LinearLayout>
