scroll+zoom android textview

最新推荐文章于 2026-01-07 19:50:22 发布

原创最新推荐文章于 2026-01-07 19:50:22 发布 · 210 阅读

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文章标签：

#android #textview #touch #zoom #scroll

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本文介绍如何在Android环境下将'Hello World'文本设置为可缩放和移动，包括使用main.xml和A1Activity.java实现纵向滚动条、记录文字块位置、响应触摸事件进行缩放和拖动操作。

目标=把helloworld的文字变成可以缩放的，并可以移动文字块[scrollable]。

测试=需要能实体手机，虚拟机似乎不能进行触摸缩放测试。

版本=android 2.3.3，target=android-10

效果图

scroll text view

zoom text view

关键点

=============main.xml

<TextView android:id="@+id/text"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:scrollbars = "vertical"

android:text="@string/hello" />

显示纵向滚动条。

=============A1Activity.java

tvPosSave.set(xt, yt);

记住文字块的位置。

关键文件代码

=============main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView android:id="@+id/text"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:scrollbars = "vertical"
        android:text="@string/hello" />

</LinearLayout>

=============A1Activity.java

package com.ex.a1205;

import android.app.Activity;
import android.graphics.Point;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.util.TypedValue;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.view.View.OnTouchListener;
import android.widget.TextView;

public class A1Activity extends Activity implements OnTouchListener {
  enum Mode {
    NONE, DRAG, ZOOM
  }

  Mode mode = Mode.NONE;
  static final int MIN_FONT_SIZE = 20;
  static final int MAX_FONT_SIZE = 120;
  PointF start = new PointF();

  Point tvPos0 = new Point();
  Point tvPos1 = new Point();
  Point tvPosSave = new Point();

  float oldDist = 1f;
  int scrWidth;
  int scrHeight;
  TextView textView;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    textView = (TextView) findViewById(R.id.text);
    loadDoc();
    textView.setOnTouchListener(this);
    Display display = ((WindowManager) getSystemService(WINDOW_SERVICE))
        .getDefaultDisplay();
    scrWidth = display.getWidth();
    scrHeight = display.getHeight();
  }

  private void loadDoc() {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i <= 30; i++) {
      sb.append("Line: ").append(i).append("\n");
    }
    textView.setText(sb.toString());
  }

  public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
      start.set(event.getX(), event.getY());
      tvPos0.set((int) event.getX(), (int) event.getY());
      mode = Mode.DRAG;
      break;
    case MotionEvent.ACTION_POINTER_DOWN:
      oldDist = spacing(event);
      if (oldDist > 10f) {
        mode = Mode.ZOOM;
      }
      break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_POINTER_UP:
      mode = Mode.NONE;
      tvPos1.set(tvPosSave.x, tvPosSave.y);
      break;
    case MotionEvent.ACTION_MOVE:
      if (mode == Mode.DRAG) {
        doScroll(event);
      } else if (mode == Mode.ZOOM) {
        doZoom(event);
      }
      break;
    }
    return true;
  }

  private void doScroll(MotionEvent event) {
    int xe = (int) event.getX();
    int ye = (int) event.getY();
    int txtHeight = textView.getLineHeight() * (textView.getLineCount() - 2);
    int xt = tvPos1.x + tvPos0.x - xe;
    int yt = tvPos1.y + tvPos0.y - ye;
    if (xt < -textView.getRight()) {
      xt = -textView.getRight() + 20;
    } else if (xt > scrWidth) {
      xt = scrWidth - 20;
    }
    if (yt < -textView.getBottom()) {
      yt = -textView.getBottom() + textView.getLineHeight();
    } else if (yt > txtHeight) {
      yt = txtHeight;
    }
    textView.scrollTo(xt, yt);
    tvPosSave.set(xt, yt);
//    log("to(", xt, ",", yt, ")"
//        , " tHt=", txtHeight
//     );
  }

  void log(Object... objs) {
    StringBuilder sb = new StringBuilder();
    for (Object obj : objs) {
      sb.append(obj);
    }
    Log.d(A1Activity.class.getSimpleName(), sb.toString());
  }

  private void doZoom(MotionEvent event) {
    float newDist = spacing(event);
    if (newDist > 10f) {
      float scale = newDist / oldDist;
      if (scale > 1) {
        scale = 1.1f;
      } else if (scale < 1) {
        scale = 0.95f;
      }
      float currSize = textView.getTextSize() * scale;
      if ((currSize < MAX_FONT_SIZE && currSize > MIN_FONT_SIZE)
          || (currSize >= MAX_FONT_SIZE && scale < 1)
          || (currSize <= MIN_FONT_SIZE && scale > 1)) {
        textView.setTextSize(TypedValue.COMPLEX_UNIT_PX, currSize);
      }
    }
  }

  /** Determine the space between the first two fingers */
  private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
  }

}