Zoom In and Out to TextView in Android - GeeksforGeeks

14 Apr, 2021
In this article, we are going to implement the zoom in and zoom out feature in TextView. As we zoom we will see the image after zoom in. Basically, we are going to learn how to increase or decrease the text size in android. A sample GIF is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Java language. 
Step 1: Create a new Project
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.  
Step 2: Working with the activity_main.xml file
Go to the activity_main.xml file and refer to the following code. Below is the code for the activity_main.xml file.
XML
<?xml version="1.0" encoding="utf-8"?><LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MainActivity">     <TextView        android:id="@+id/zoomin"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_marginTop="40dp"        android:gravity="center"        android:text="GeeksForGeeks"        android:textColor="#CE1D59"        android:textSize="32sp" />     </LinearLayout>
Step 3: Working with the MainActivity.java file
Go to the MainActivity.java file and refer to the following code. Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.
Java
import android.os.Bundle;import android.view.MotionEvent;import android.view.View;import android.widget.TextView; import androidx.appcompat.app.AppCompatActivity; public class MainActivity extends AppCompatActivity implements View.OnTouchListener {     TextView text;    final static float move = 200;    float ratio = 1.0f;    int bastDst;    float baseratio;     @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        text = findViewById(R.id.zoomin);        text.setTextSize(ratio + 15);    }     @Override    public boolean onTouchEvent(MotionEvent event) {        if (event.getPointerCount() == 2) {            int action = event.getAction();            int mainaction = action & MotionEvent.ACTION_MASK;            if (mainaction == MotionEvent.ACTION_POINTER_DOWN) {                bastDst = getDistance(event);                baseratio = ratio;            } else {                // if ACTION_POINTER_UP then after finding the distance                // we will increase the text size by 15                float scale = (getDistance(event) - bastDst) / move;                float factor = (float) Math.pow(2, scale);                ratio = Math.min(1024.0f, Math.max(0.1f, baseratio * factor));                text.setTextSize(ratio + 15);            }        }        return true;    }     // get distance between the touch event    private int getDistance(MotionEvent event) {        int dx = (int) (event.getX(0) - event.getX(1));        int dy = (int) (event.getY(0) - event.getY(1));        return (int) Math.sqrt(dx * dx + dy * dy);    }     @Override    public boolean onTouch(View v, MotionEvent event) {        return false;    }}
Output:
Android
Java
Java
Android
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