How to create an activity without 'setContentView(R.layout.main)'
You can pass setContentView() any form of view, to be the root view of your layout. Below is a dynamically built LinearLayout with a Button and your myView
.
public class Example extends Activity {
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
LinearLayout layout = new LinearLayout(this);
// Define the LinearLayout's characteristics
layout.setGravity(Gravity.CENTER);
layout.setOrientation(LinearLayout.VERTICAL);
// Set generic layout parameters
LayoutParams params = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
Button button = new Button(this);
button.setText("Button!");
layout.addView(button, params); // Modify this
myView custom = new myView(this);
layout.addView(custom, params); // Of course, this too
setContentView(layout);
}
}
Understand that you can only add child views to your root view if you pass setContentView() a ViewGroup; like RelativeLayout, LinearLayout, etc. In other words you cannot do this:
myView custom = new myView(this);
Button button = new Button(this);
button.setText("Button!");
custom.addView(button);
// Nope! Method "addView()" does not exist for a regular View...
setContentView(custom);
Also, naming convention suggests that each word in a class name should have the first letter capitalized. So myView
ought to be MyView
, at a minimum it makes your code easier to read for other programmers and the compiler will highlight your class variables with the correct color.
user1472757
Updated on June 23, 2020Comments
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user1472757 about 4 years
I know its possible to create activities by doing something like the code bellow, where the view is not set from xml file but like this: setContentView(new myView(this));
What i don't understand is how to use this code but still have the ability to customize it, for instance if i wanted to add a button to the code bellow, how would i do it, because i cant simply add one to an xml layout can i?
ANY GOOD ANSWERS TO THIS WILL VERY MUCH APPRECIATED thanks in advance!
package com.faceapp; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.PointF; import android.media.FaceDetector; import android.media.FaceDetector.Face; import android.os.Bundle; import android.view.View; public class FaceappActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setContentView(R.layout.main); setContentView(new myView(this)); } private class myView extends View{ private int imageWidth, imageHeight; private int numberOfFace = 5; private FaceDetector myFaceDetect; private FaceDetector.Face[] myFace; float myEyesDistance; int numberOfFaceDetected; Bitmap myBitmap; public myView(Context context) { super(context); // TODO Auto-generated constructor stub BitmapFactory.Options BitmapFactoryOptionsbfo = new BitmapFactory.Options(); BitmapFactoryOptionsbfo.inPreferredConfig = Bitmap.Config.RGB_565; myBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.face5, BitmapFactoryOptionsbfo); imageWidth = myBitmap.getWidth(); imageHeight = myBitmap.getHeight(); myFace = new FaceDetector.Face[numberOfFace]; myFaceDetect = new FaceDetector(imageWidth, imageHeight, numberOfFace); numberOfFaceDetected = myFaceDetect.findFaces(myBitmap, myFace); } @Override protected void onDraw(Canvas canvas) { // TODO Auto-generated method stub canvas.drawBitmap(myBitmap, 0, 0, null); Paint myPaint = new Paint(); myPaint.setColor(Color.GREEN); myPaint.setStyle(Paint.Style.STROKE); myPaint.setStrokeWidth(3); for(int i=0; i < numberOfFaceDetected; i++) { Face face = myFace[i]; PointF myMidPoint = new PointF(); face.getMidPoint(myMidPoint); myEyesDistance = face.eyesDistance(); canvas.drawRect( (int)(myMidPoint.x - myEyesDistance), (int)(myMidPoint.y - myEyesDistance), (int)(myMidPoint.x + myEyesDistance), (int)(myMidPoint.y + myEyesDistance), myPaint); } } } }
^^^^^^^^^^^^^^^ Answered
How to position the button and imageview? (Ideally using relative layout) The picture bellow shows you what i mean: (Ignore that the image is re-sized)
NEW CODE:
package com.test; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.PointF; import android.media.FaceDetector; import android.media.FaceDetector.Face; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.LinearLayout; public class TesttActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); LinearLayout layout = new LinearLayout(this); Button button = new Button(this); button.setText("Button!"); layout.addView(button); myView custom = new myView(this); layout.addView(custom); setContentView(layout); } private class myView extends View{ private int imageWidth, imageHeight; private int numberOfFace = 5; private FaceDetector myFaceDetect; private FaceDetector.Face[] myFace; float myEyesDistance; int numberOfFaceDetected; Bitmap myBitmap; public myView(Context context) { super(context); // TODO Auto-generated constructor stub BitmapFactory.Options BitmapFactoryOptionsbfo = new BitmapFactory.Options(); BitmapFactoryOptionsbfo.inPreferredConfig = Bitmap.Config.RGB_565; myBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.face5, BitmapFactoryOptionsbfo); imageWidth = myBitmap.getWidth(); imageHeight = myBitmap.getHeight(); myFace = new FaceDetector.Face[numberOfFace]; myFaceDetect = new FaceDetector(imageWidth, imageHeight, numberOfFace); numberOfFaceDetected = myFaceDetect.findFaces(myBitmap, myFace); } @Override protected void onDraw(Canvas canvas) { // TODO Auto-generated method stub canvas.drawBitmap(myBitmap, 0, 0, null); Paint myPaint = new Paint(); myPaint.setColor(Color.GREEN); myPaint.setStyle(Paint.Style.STROKE); myPaint.setStrokeWidth(3); for(int i=0; i < numberOfFaceDetected; i++) { Face face = myFace[i]; PointF myMidPoint = new PointF(); face.getMidPoint(myMidPoint); myEyesDistance = face.eyesDistance(); canvas.drawRect( (int)(myMidPoint.x - myEyesDistance), (int)(myMidPoint.y - myEyesDistance), (int)(myMidPoint.x + myEyesDistance), (int)(myMidPoint.y + myEyesDistance), myPaint); } } } }
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user1472757 about 12 yearsThanks alot Sam, I got it working. My only issue now is positioning the items, such as the button and the imageView created by the myView/onDraw. Ill update the question to show you what i mean. :)
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user1472757 about 12 yearsIm guessing you can do it by RelativeLayout layout = new RelativeLayout(this); But how can I position the button and imageview?, Thanks
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Sam about 12 years@user1472757 I updated the code in my answer. Each attribute can either be set in XML or Java, in the Developer's Guide the XML attributes have a "related method" that is a synonymous Java function (ie for LinearLayout
android:orientation
issetOrientation()
).