How to make a Textview display a number?
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I'm new to Android development. I tried to make a Textview display a text or number and it crashes. Please Help. :(
This is the button in activity_main.xml:

    <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignLeft="@+id/textView1"
            android:layout_alignParentBottom="true"
            android:text="@string/Change" 
            android:onClick="change"/>
and this is the Main Activity:

    public void change(){
        	TextView tv = new TextView(this);
        	tv.setText("" + 4);
        }
the application crashes when i start it. I wanted to create a basic calculator with two text boxes and a button which when pressed adds the value in two text boxes and display it. can anybody tell me where I am going wrong with the code?