How do I set an Android ProgressBar's Size programmatically?

You can use LayoutParams to change width and height to whatever you want.

ProgressBar progressBar = new ProgressBar(teste.this, null, android.R.attr.progressBarStyleHorizontal);

            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(300, 10);

            progressBar.setLayoutParams(params );
            LinearLayout test = new LinearLayout(getApplicationContext());
            test.addView(progressBar);
            setContentView(test);

Also when you add a view, you can use this code: test.addView(progressBar,50,50); where the first parameter is width and the second is height.

You can also set the size of your progressbar from within the xml, just use android:maxHeight, android:minHeight, android:minWidth and android:maxWidth properties inside your ProgressBar tag.

for instance, this will set the height of the progressbar to 35dip and width to 10dip,

   <ProgressBar
    android:id="@+id/progressBar1"
    style="?android:attr/progressBarStyleLarge"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"

    android:layout_centerVertical="true"
    android:layout_marginLeft="60dip"
    android:maxHeight="35dip"
    android:minHeight="35dip"

    android:minWidth="10dip"
    android:maxWidth="10dip"

    android:visibility="visible" />

In the xml, set the style, for example,

style="?android:attr/progressBarStyleLarge"

<ProgressBar
                        android:id="@+id/progressBar3"
                        style="?android:attr/progressBarStyleLarge"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_centerInParent="true" />