Android Studio預設建立的view學習筆記
阿新 • • 發佈:2019-01-24
建立檔案
使用Studio預設建立自定義檢視會自動建立3個檔案:
java檔案MyView
直接xml檔案的myView
屬性檔案attrs_my_view(屬性檔案不用全命名是attrs)
分別解釋
Java檔案
首先顯示的是大量的自定義屬性
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個重寫的帶有不同引數的構造方法
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);
}
各種自定義屬性的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;
}
重寫onDraw方法自定義檢視
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);
}
}
初始化資料的兩個方法(寫法超讚)
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是儲存屬性的陣列,而MyView_exampleDimension這種寫法的MyView就是自定義屬性的命名name屬性
沒事巴巴幾句:終於能看懂系統自動建立的模板之一了,世界有愛了