android imageView : setting drag and pinch zoom parameters

Question

我目前正在为 Android(我的第一个应用程序)开发一个应用程序，它可以让用户查看地铁 map 并能够捏缩放和拖动。

我目前正在修改 Hello Android，第 3 版中的代码，并让捏缩放和拖动工作。我使用 Matrix 作为我的布局比例。

但是我现在有 3 个问题:

1. 我尝试了很多方法来限制拖动参数，但我似乎无法阻止它被拖离父 View (实际上可以从 View 中消失)。我尝试在 XML 文件中设置布局参数，但它不起作用。

2. 我可以很好地捏缩放，但我又遇到了麻烦，限制缩放量。我正在尝试设置 max_zoom 和 min_zoom 来限制缩放值(我将在之后发布我的代码)

3. 我也很难在我的图像上绘制一个坐标，以便人们可以点击某些部分(这样做的重点是让用户点击 map 上的一个站点并查看有关它的信息)

我觉得我遇到了麻烦，因为我使用的是矩阵刻度。

这是我当前的代码:

Touch.java

package org.example.touch;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.GridView;
import android.widget.ImageView;

public class Touch extends Activity implements OnTouchListener {
private static final String TAG = "Touch";

private static final float MIN_ZOOM = 1.0f;
private static final float MAX_ZOOM = 5.0f;

// These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();

// We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;

// Remember some things for zooming
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;

@Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);
   ImageView view = (ImageView) findViewById(R.id.imageView);
   //view.setLayoutParams(new GridView.LayoutParams(85, 85));
   view.setScaleType(ImageView.ScaleType.FIT_CENTER);
   view.setOnTouchListener(this);   
}

public boolean onTouch(View v, MotionEvent event) {
   ImageView view = (ImageView) v;
   view.setScaleType(ImageView.ScaleType.MATRIX);
   float scale;

   // Dump touch event to log
   dumpEvent(event);

   // Handle touch events here...
   switch (event.getAction() & MotionEvent.ACTION_MASK) {

   case MotionEvent.ACTION_DOWN: //first finger down only
      savedMatrix.set(matrix);
      start.set(event.getX(), event.getY());
      Log.d(TAG, "mode=DRAG" );
      mode = DRAG;
      break;
   case MotionEvent.ACTION_UP: //first finger lifted
   case MotionEvent.ACTION_POINTER_UP: //second finger lifted
      mode = NONE;
      Log.d(TAG, "mode=NONE" );
      break;
   case MotionEvent.ACTION_POINTER_DOWN: //second finger down
      oldDist = spacing(event);
      Log.d(TAG, "oldDist=" + oldDist);
      if (oldDist > 5f) {
         savedMatrix.set(matrix);
         midPoint(mid, event);
         mode = ZOOM;
         Log.d(TAG, "mode=ZOOM" );
      }
      break;

   case MotionEvent.ACTION_MOVE: 
      if (mode == DRAG) { //movement of first finger
         matrix.set(savedMatrix);
         if (view.getLeft() >= -392){
            matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);
         }
      }
      else if (mode == ZOOM) { //pinch zooming
         float newDist = spacing(event);
         Log.d(TAG, "newDist=" + newDist);
         if (newDist > 5f) {
            matrix.set(savedMatrix);
            scale = newDist / oldDist; **//thinking i need to play around with this value to limit it**
            matrix.postScale(scale, scale, mid.x, mid.y);
         }
      }
      break;
   }

   // Perform the transformation
   view.setImageMatrix(matrix);

   return true; // indicate event was handled
}

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);
}

private void midPoint(PointF point, MotionEvent event) {
   float x = event.getX(0) + event.getX(1);
   float y = event.getY(0) + event.getY(1);
   point.set(x / 2, y / 2);
}

/** Show an event in the LogCat view, for debugging */
private void dumpEvent(MotionEvent event) {
   String names[] = { "DOWN" , "UP" , "MOVE" , "CANCEL" , "OUTSIDE" ,
      "POINTER_DOWN" , "POINTER_UP" , "7?" , "8?" , "9?" };
   StringBuilder sb = new StringBuilder();
   int action = event.getAction();
   int actionCode = action & MotionEvent.ACTION_MASK;
   sb.append("event ACTION_" ).append(names[actionCode]);
   if (actionCode == MotionEvent.ACTION_POINTER_DOWN
         || actionCode == MotionEvent.ACTION_POINTER_UP) {
      sb.append("(pid " ).append(
      action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
      sb.append(")" );
   }
   sb.append("[" );
   for (int i = 0; i < event.getPointerCount(); i++) {
      sb.append("#" ).append(i);
      sb.append("(pid " ).append(event.getPointerId(i));
      sb.append(")=" ).append((int) event.getX(i));
      sb.append("," ).append((int) event.getY(i));
      if (i + 1 < event.getPointerCount())
         sb.append(";" );
   }
   sb.append("]" );
   Log.d(TAG, sb.toString());
}
}

ma​​in.xml(相当简单，没什么复杂的):

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" >
<ImageView android:id="@+id/imageView"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:src="@drawable/map"
     android:scaleType="matrix" >
</ImageView>
</FrameLayout>

AndroidManifest.xml(只加了主题所以没有标题栏，全屏)

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="org.example.touch"
  android:versionCode="7"
  android:versionName="1.0" >
<application android:icon="@drawable/icon" android:label="@string/app_name" android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >
  <activity android:name=".Touch"
        android:label="@string/app_name" >
     <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
     </intent-filter>
  </activity>
</application>
<uses-sdk android:minSdkVersion="3" android:targetSdkVersion="7" />
</manifest>

Answer 1

我刚刚创建了这个:

https://github.com/jasonpolites/gesture-imageview

可能对某人有用...