Android(安卓)Studio默认创建的view学习笔记

创建文件

使用Studio默认创建自定义视图会自动创建3个文件：
java文件MyView
直接xml文件的myView
属性文件attrs_my_view（属性文件不用全命名是attrs）

分别解释

Java文件

首先显示的是大量的自定义属性

 private String mExampleString; // TODO: use a default from R.string...    private int mExampleColor = Color.RED; // TODO: use a default from R.color...    private float mExampleDimension = 0; // TODO: use a default from R.dimen...    private Drawable mExampleDrawable;    private TextPaint mTextPaint;    private float mTextWidth;    private float mTextHeight;

3个重写的带有不同参数的构造方法

public MyView(Context context) {        super(context);        init(null, 0);    }    public MyView(Context context, AttributeSet attrs) {        super(context, attrs);        init(attrs, 0);    }    public MyView(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        init(attrs, defStyle);    }

各种自定义属性的get和set方法

public String getExampleString() {        return mExampleString;    }    /** * Sets the view's example string attribute value. In the example view, this string * is the text to draw. * * @param exampleString The example string attribute value to use. */    public void setExampleString(String exampleString) {        mExampleString = exampleString;        invalidateTextPaintAndMeasurements();    }    /** * Gets the example color attribute value. * * @return The example color attribute value. */    public int getExampleColor() {        return mExampleColor;    }    /** * Sets the view's example color attribute value. In the example view, this color * is the font color. * * @param exampleColor The example color attribute value to use. */    public void setExampleColor(int exampleColor) {        mExampleColor = exampleColor;        invalidateTextPaintAndMeasurements();    }    /** * Gets the example dimension attribute value. * * @return The example dimension attribute value. */    public float getExampleDimension() {        return mExampleDimension;    }    /** * Sets the view's example dimension attribute value. In the example view, this dimension * is the font size. * * @param exampleDimension The example dimension attribute value to use. */    public void setExampleDimension(float exampleDimension) {        mExampleDimension = exampleDimension;        invalidateTextPaintAndMeasurements();    }    /** * Gets the example drawable attribute value. * * @return The example drawable attribute value. */    public Drawable getExampleDrawable() {        return mExampleDrawable;    }    /** * Sets the view's example drawable attribute value. In the example view, this drawable is * drawn above the text. * * @param exampleDrawable The example drawable attribute value to use. */    public void setExampleDrawable(Drawable exampleDrawable) {        mExampleDrawable = exampleDrawable;    }

重写onDraw方法自定义视图

protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        // TODO: consider storing these as member variables to reduce        // allocations per draw cycle.        int paddingLeft = getPaddingLeft();        int paddingTop = getPaddingTop();        int paddingRight = getPaddingRight();        int paddingBottom = getPaddingBottom();        int contentWidth = getWidth() - paddingLeft - paddingRight;        int contentHeight = getHeight() - paddingTop - paddingBottom;        // Draw the text.        canvas.drawText(mExampleString,                paddingLeft + (contentWidth - mTextWidth) / 2,                paddingTop + (contentHeight + mTextHeight) / 2,                mTextPaint);        // Draw the example drawable on top of the text.        if (mExampleDrawable != null) {            mExampleDrawable.setBounds(paddingLeft, paddingTop,                    paddingLeft + contentWidth, paddingTop + contentHeight);            mExampleDrawable.draw(canvas);        }    }

初始化数据的两个方法（写法超赞）

private void init(AttributeSet attrs, int defStyle) {        // Load attributes        final TypedArray a = getContext().obtainStyledAttributes(                attrs, R.styleable.MyView, defStyle, 0);        mExampleString = a.getString(                R.styleable.MyView_exampleString);        mExampleColor = a.getColor(                R.styleable.MyView_exampleColor,                mExampleColor);        // Use getDimensionPixelSize or getDimensionPixelOffset when dealing with        // values that should fall on pixel boundaries.        mExampleDimension = a.getDimension(                R.styleable.MyView_exampleDimension,                mExampleDimension);        if (a.hasValue(R.styleable.MyView_exampleDrawable)) {            mExampleDrawable = a.getDrawable(                    R.styleable.MyView_exampleDrawable);            mExampleDrawable.setCallback(this);        }        a.recycle();        // Set up a default TextPaint object        mTextPaint = new TextPaint();        mTextPaint.setFlags(Paint.ANTI_ALIAS_FLAG);        mTextPaint.setTextAlign(Paint.Align.LEFT);        // Update TextPaint and text measurements from attributes        invalidateTextPaintAndMeasurements();    }    private void invalidateTextPaintAndMeasurements() {        mTextPaint.setTextSize(mExampleDimension);        mTextPaint.setColor(mExampleColor);        mTextWidth = mTextPaint.measureText(mExampleString);        Paint.FontMetrics fontMetrics = mTextPaint.getFontMetrics();        mTextHeight = fontMetrics.bottom;    }

TypedArray是存储属性的数组，而MyView_exampleDimension这种写法的MyView就是自定义属性的命名name属性

没事巴巴几句：终于能看懂系统自动创建的模板之一了，世界有爱了

创建文件

分别解释

Java文件

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