TextView_第一节_改变内容和字号

阿弥陀佛:

要有定力哦 ! ! !

学完这个个系列，自定义View就So Easy...
主要是逐步分析TextView源码，分析完成后，你就能够彻底了解TextView，想怎么玩就怎么玩。。。

实现的主要内容:

继承View，实现基本TextView功能:更改内容和字体大小。

步骤1： 定义atts.xml文件:

步骤2:解析属性文件

    //TypedArray:一组容器用来保存属性的数组
    TypedArray a = theme.obtainStyledAttributes(attrs,
            R.styleable.TextViewAppearance, defStyleAttr, defStyleRes);
    TypedArray appearance = null;
    int ap = a.getResourceId(
            R.styleable.TextViewAppearance_textAppearance, -1);
    a.recycle();
    if (ap != -1) {
        appearance = theme.obtainStyledAttributes(
                ap, R.styleable.TextAppearance);
    }
    if (appearance != null) {
        int n = appearance.getIndexCount();
        for (int i = 0; i < n; i++) {
            int attr = appearance.getIndex(i);
            switch (attr) {
                case R.styleable.TextView_text:
                    text = a.getText(attr);
                    break;
            }
        }
    }

步骤3：初始化TextPaint

//TextPaint主要用来存储字体大小、颜色等属性
private TextPaint mPaint;
mPaint = new TextPaint();
mPaint.setColor(getResources().getColor(R.color.red));
mPaint.setTextSize(DensityUtil.dip2px(getContext(), textSize));

步骤4：调用onDraw绘制文字

canvas.drawText(text.toString(), getWidth() / 2, getHeight() / 2, mPaint);

步骤5:定义改变内容和字体大小的方法:

public CharSequence getText() {
    return text;
}

public void setText(CharSequence text) {
    this.text = text;
    invalidate();
}

public int getTextSize() {
    return textSize;

}

public void setTextSize(int textSize) {
    this.textSize = textSize;
    mPaint.setTextSize(DensityUtil.dip2px(getContext(),textSize));
    invalidate();
}

自定义TextView完整代码:

    public class LincolnTextView extends View {
    private CharSequence text;
    private TextPaint mPaint;
    private int textSize = 30;


    public LincolnTextView(Context context) {
        this(context, null);
    }

    public LincolnTextView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, R.attr.textViewStyle);
    }

    public LincolnTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
    }

    public LincolnTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        CharSequence text = "AAAA";
        final Resources.Theme theme = context.getTheme();


        TypedArray a = theme.obtainStyledAttributes(attrs,
                R.styleable.TextViewAppearance, defStyleAttr, defStyleRes);
        TypedArray appearance = null;
        int ap = a.getResourceId(
                R.styleable.TextViewAppearance_textAppearance, -1);
        a.recycle();
        if (ap != -1) {
            appearance = theme.obtainStyledAttributes(
                    ap, R.styleable.TextAppearance);
        }
        if (appearance != null) {
            int n = appearance.getIndexCount();
            for (int i = 0; i < n; i++) {
                int attr = appearance.getIndex(i);
                switch (attr) {
                    case R.styleable.TextView_text:
                        text = a.getText(attr);
                        break;
                }
            }
        }
        mPaint = new TextPaint();
        mPaint.setColor(getResources().getColor(R.color.red));
        mPaint.setTextSize(DensityUtil.dip2px(getContext(), textSize));
        setText(text);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.drawText(text.toString(), getWidth() / 2, getHeight() / 2, mPaint);

    }

    public CharSequence getText() {
        return text;
    }

    public void setText(CharSequence text) {
        this.text = text;
        invalidate();
    }

    public int getTextSize() {
        return textSize;

    }

    public void setTextSize(int textSize) {
        this.textSize = textSize;
        mPaint.setTextSize(DensityUtil.dip2px(getContext(),textSize));
        invalidate();
    }
}

步骤6：定义布局文件:

步骤7：改变字号和内容:

    textView = (LincolnTextView) findViewById(R.id.lincolnTextView);
    button = (Button)findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            textView.setText("BBBB");
            textView.setTextSize(20);
        }
    });

Github源码:

View_2_TextView
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