Why Am I Getting the \'The Specified Child Already Has a Parent\' Error in Android?-javaTutorial-php.cn

Why Am I Getting the \'The Specified Child Already Has a Parent\' Error in Android?

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Release： 2024-10-30 13:22:02

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Why Am I Getting the

Troubleshooting Android Error: "The Specified Child Already Has a Parent"

When switching frequently between layouts, you may encounter the error "The specified child already has a parent. You must call removeView() on the child's parent first (Android)." This occurs when a view, such as a TextView or EditText, is added to a layout that has already been attached to the application's content view.

For instance, consider the following code where a layout is created and switched frequently:

<code class="java">private void ConsoleWindow() {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            // Create a new layout (LinearLayout).
            LinearLayout layout = new LinearLayout(getApplicationContext());
            layout.setOrientation(LinearLayout.VERTICAL);

            // Add a TextView to the layout.
            layout.addView(tv);

            // Add an EditText to the layout.
            et.setHint("Enter Command");
            layout.addView(et);

            // Set the content view to the new layout.
            setContentView(layout);
        }
    });
}</code>

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The problem arises when the setContentView() method is called twice with different layouts. The first time, there is no issue because the LinearLayout layout is added to the content view for the first time. However, during subsequent calls to setContentView(), the LinearLayout layout still contains its children (TextView and EditText). As the LinearLayout object already has a parent (the content view), adding it again throws the "The specified child already has a parent" error.

Solution:

The solution is to remove the children (TextView and EditText) from the LinearLayout layout before adding it to the content view a second time. Here's the modified code:

<code class="java">private void ConsoleWindow() {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            // Create a new layout (LinearLayout).
            LinearLayout layout = new LinearLayout(getApplicationContext());
            layout.setOrientation(LinearLayout.VERTICAL);

            // Remove the TextView from its parent (if it has one).
            if (tv.getParent() != null) {
                ((ViewGroup) tv.getParent()).removeView(tv);
            }
            
            // Add the TextView to the layout.
            layout.addView(tv);

            // Remove the EditText from its parent (if it has one).
            if (et.getParent() != null) {
                ((ViewGroup) et.getParent()).removeView(et);
            }
            
            // Add the EditText to the layout.
            et.setHint("Enter Command");
            layout.addView(et);

            // Set the content view to the new layout.
            setContentView(layout);
        }
    });
}</code>

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By removing the children from their previous parent before adding them to the new LinearLayout layout, you ensure that they are not attached to multiple parents simultaneously, resolving the "The specified child already has a parent" error.

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