Initializing and setting params of Button programatically

Question

I am trying to initialize and set the height and width of 5 buttons programmatically. Below is my code, XML and LogCat.

public class Puzzle extends Activity {

    Button btn1, btn2, btn3, btn4, btn5;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.z1to5);

        RelativeLayout relativelayout = (RelativeLayout)findViewById(R.id.relativelayout);
        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(50, 50);

        btn1 = (Button)findViewById(R.id.btn1);
        btn2 = (Button)findViewById(R.id.btn2);
        btn3 = (Button)findViewById(R.id.btn3);
        btn4 = (Button)findViewById(R.id.btn4);
        btn5 = (Button)findViewById(R.id.btn5);

        btn1.setLayoutParams(params);
        btn2.setLayoutParams(params);
        btn3.setLayoutParams(params);
        btn4.setLayoutParams(params);
        btn5.setLayoutParams(params);

        relativelayout.addView(btn1);
        relativelayout.addView(btn2);
        relativelayout.addView(btn3);
        relativelayout.addView(btn4);
        relativelayout.addView(btn5);
    }
}

<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/relativelayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/btn1" />

    <Button
        android:id="@+id/btn2" />

    <Button
        android:id="@+id/btn3" />

    <Button
        android:id="@+id/btn4" />

    <Button
        android:id="@+id/btn5" />
</RelativeLayout>

This is my first time trying to make a layout in Java. I've always done it in XML. Below is the LogCat error that I am getting.

LogCat

11-21 17:22:13.590: E/AndroidRuntime(2639): Process: matt.lyons.tileslider, PID: 2639
11-21 17:22:13.590: E/AndroidRuntime(2639): java.lang.RuntimeException: Unable to start activity ComponentInfo{matt.lyons.tileslider/matt.lyons.tileslider.Puzzle}: java.lang.RuntimeException: Binary XML file line #8: You must supply a layout_width attribute.
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.ActivityThread.access$700(ActivityThread.java:135)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.os.Handler.dispatchMessage(Handler.java:102)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.os.Looper.loop(Looper.java:137)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at java.lang.reflect.Method.invokeNative(Native Method)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at java.lang.reflect.Method.invoke(Method.java:515)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at dalvik.system.NativeStart.main(Native Method)
11-21 17:22:13.590: E/AndroidRuntime(2639): Caused by: java.lang.RuntimeException: Binary XML file line #8: You must supply a layout_width attribute.
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.content.res.TypedArray.getLayoutDimension(TypedArray.java:492)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.view.ViewGroup$LayoutParams.setBaseAttributes(ViewGroup.java:5948)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.view.ViewGroup$MarginLayoutParams.<init>(ViewGroup.java:6117)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.widget.RelativeLayout$LayoutParams.<init>(RelativeLayout.java:1225)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.widget.RelativeLayout.generateLayoutParams(RelativeLayout.java:1062)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.widget.RelativeLayout.generateLayoutParams(RelativeLayout.java:82)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:757)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.view.LayoutInflater.inflate(LayoutInflater.java:353)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:290)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.Activity.setContentView(Activity.java:1928)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at matt.lyons.tileslider.Puzzle.onCreate(Puzzle.java:17)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.Activity.performCreate(Activity.java:5243)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-21 17:22:13.590: E/AndroidRuntime(2639):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
11-21 17:22:13.590: E/AndroidRuntime(2639):     ... 11 more

What am I doing wrong?

Answer 1

If you are going to create views programmatically do not use method setContentView() with layoutId parameter, because it calls LayoutInflater to create views from XML file and can't do it because your XML is not correct. So try something like this:

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    LinearLayout rootLayout = new LinearLayout(getApplicationContext());
    rootLayout.setOrientation(LinearLayout.VERTICAL);

    //Convert DIPs to Pixels
    int dp = 50;
    int px = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, getResources().getDisplayMetrics());

    LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(px * 4, px);

    for (int i = 1; i < 6; i++) {
        Button button = new Button(getApplicationContext());
        button.setLayoutParams(layoutParams);
        button.setText("Button " + i);
        rootLayout.addView(button);
    }

    setContentView(rootLayout);
}