Android如何实现字体的缩放

最新推荐文章于 2022-09-05 10:58:36 发布

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本文介绍了一种通过实现自定义监听器来调整Android中TextView文本大小的方法。该监听器能够响应双指缩放手势，根据用户的手势调整TextView内的字体大小。

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1、首先实现一个ZoomListenter类

package com.example.mpcc.mqttandroid.Zoom;


import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.TextView;

public class ZoomListenter implements OnTouchListener {

    private int mode = 0;
    float oldDist;
    float textSize = 0;
    TextView textView = null;

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        textView = (TextView) v;
        if (textSize == 0) {
            textSize = textView.getTextSize();
        }
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                mode = 1;
                break;
            case MotionEvent.ACTION_UP:
                mode = 0;
                break;
            case MotionEvent.ACTION_POINTER_UP:
                mode -= 1;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                oldDist = spacing(event);
                mode += 1;
                break;

            case MotionEvent.ACTION_MOVE:
                if (mode >= 2) {
                    float newDist = spacing(event);
                    if (newDist > oldDist + 1) {
                        zoom(newDist / oldDist);
                        oldDist = newDist;
                    }
                    if (newDist < oldDist - 1) {
                        zoom(newDist / oldDist);
                        oldDist = newDist;
                    }
                }
                break;
        }
        return true;
    }

    private void zoom(float f) {
        textView.setTextSize(textSize *= f);
    }

    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float)Math.sqrt(x * x + y * y);
    }

}

2、调用

        TextView shouye = (TextView) system_introduction.findViewById(R.id.shouye);
        shouye.setOnTouchListener(new ZoomListenter());