How to Correctly Add a TextView to a LinearLayout Programmatically in Android?

Adding a TextView to a LinearLayout Programmatically in Android

In Android development, it is often necessary to add views dynamically to a layout defined in an XML file. This article explores the process of adding a TextView to a pre-defined LinearLayout in code.

Problem:

The user attempted to add a TextView to a LinearLayout defined in XML using the following code:

<code class="xml">View linearLayout = findViewById(R.id.info);
TextView valueTV = new TextView(this);
valueTV.setText("hallo hallo");
valueTV.setId(5);
valueTV.setLayoutParams(new LayoutParams(
        LayoutParams.FILL_PARENT,
        LayoutParams.WRAP_CONTENT));

((LinearLayout) linearLayout).addView(valueTV);</code>

However, this code resulted in a ClassCastException exception:

java.lang.ClassCastException: android.widget.TextView

Solution:

The error occurred due to an incorrect cast of the linearLayout variable. To access the LinearLayout, it should be cast as a LinearLayout explicitly:

<code class="xml">LinearLayout linearLayout = (LinearLayout)findViewById(R.id.info);
...
linearLayout.addView(valueTV);</code>

Additionally, the LayoutParams instance should be created using LinearLayout.LayoutParams instead of LayoutParams.

Corrected Code:

<code class="xml">LinearLayout linearLayout = (LinearLayout)findViewById(R.id.info);

TextView valueTV = new TextView(this);
valueTV.setText("hallo hallo");
valueTV.setId(5);
valueTV.setLayoutParams(new LinearLayout.LayoutParams(
        LinearLayout.LayoutParams.FILL_PARENT,
        LinearLayout.LayoutParams.WRAP_CONTENT));

linearLayout.addView(valueTV);</code>

By making these changes, the TextView will be successfully added to the LinearLayout.

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