Android – How To Create a Rotating Wheel Control

androidandroid-animationanimationimage-rotationrotation

I am trying to implement the Rotatory wheel in android, just like the image displayed below.I came across the tutorial from this link. But i want to implement just as shown in the below image.The wheel consists of individual images.Does anybody have any idea regarding this implementation?? Any help would be appreciated.

enter image description here

Thanks in advance.

Akash

Best Solution

To do this from scratch, you would need a way to transform your touch coordinates, into polar coordinates (to have the rotation angle). This can be done easily like this:

private float cartesianToPolar(float x, float y) {
  return (float) -Math.toDegrees(Math.atan2(x - 0.5f, y - 0.5f));
}

To rotate the imageview, or the element you are using to display your knob, you can use a matrix like this:

Matrix matrix=new Matrix();
ivRotor.setScaleType(ScaleType.MATRIX);   
matrix.postRotate((float) deg, m_nWidth/2, m_nHeight/2);//getWidth()/2, getHeight()/2);
ivRotor.setImageMatrix(matrix);

Where deg is the angle and ivRobor is the knob imageview.

A complete working sample for Android, is available on Google code at: https://code.google.com/p/android-rotaryknob-view/

Related Solutions

Android – How to save an activity state using the save instance state

You need to override onSaveInstanceState(Bundle savedInstanceState) and write the application state values you want to change to the Bundle parameter like this:

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
  super.onSaveInstanceState(savedInstanceState);
  // Save UI state changes to the savedInstanceState.
  // This bundle will be passed to onCreate if the process is
  // killed and restarted.
  savedInstanceState.putBoolean("MyBoolean", true);
  savedInstanceState.putDouble("myDouble", 1.9);
  savedInstanceState.putInt("MyInt", 1);
  savedInstanceState.putString("MyString", "Welcome back to Android");
  // etc.
}

The Bundle is essentially a way of storing a NVP ("Name-Value Pair") map, and it will get passed in to onCreate() and also onRestoreInstanceState() where you would then extract the values from activity like this:

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);
  // Restore UI state from the savedInstanceState.
  // This bundle has also been passed to onCreate.
  boolean myBoolean = savedInstanceState.getBoolean("MyBoolean");
  double myDouble = savedInstanceState.getDouble("myDouble");
  int myInt = savedInstanceState.getInt("MyInt");
  String myString = savedInstanceState.getString("MyString");
}

Or from a fragment.

@Override
public void onViewStateRestored(@Nullable Bundle savedInstanceState) {
    super.onViewStateRestored(savedInstanceState);
    // Restore UI state from the savedInstanceState.
    // This bundle has also been passed to onCreate.
    boolean myBoolean = savedInstanceState.getBoolean("MyBoolean");
    double myDouble = savedInstanceState.getDouble("myDouble");
    int myInt = savedInstanceState.getInt("MyInt");
    String myString = savedInstanceState.getString("MyString");
}

You would usually use this technique to store instance values for your application (selections, unsaved text, etc.).

Android – How to center text horizontally and vertically in a TextView

I'm assuming you're using XML layout.

<TextView  
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:gravity="center"
    android:text="@string/**yourtextstring**"
/>

You can also use gravity center_vertical or center_horizontal according to your need.

and as @stealthcopter commented in java: .setGravity(Gravity.CENTER);

Best Solution

Related Solutions

Android – How to save an activity state using the save instance state

Android – How to center text horizontally and vertically in a TextView

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