Android tablelayout view does not appear

问题

New to android programming.

I have a layout XML, to which I want to add a list (with items from a database), formatted as a table.

Here's the code:

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.edit_cat);

        DatabaseHandler db = new DatabaseHandler(this);
        List<Category> allCategories = db.getAllCategories();

        //Get the main layout from XML
        LinearLayout mainLayout = (LinearLayout) findViewById(R.id.edit_cat);

        //Create table layout for the categories
        TableLayout catList = new TableLayout(this);

        //Iterate the categories, and organize in tables
        for (Category category : allCategories) {
            TableRow tr = new TableRow(this);

            //Display category name
            TextView name = new TextView(this);
            name.setLayoutParams(new LayoutParams(                      
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT));

            name.setText(category.getName());


            //Display category type
            TextView type = new TextView(this);
            type.setText(category.getType());
            type.setLayoutParams(new LayoutParams(
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT));

            //Display edit button
            Button btnEdit = new Button(this);
            btnEdit.setText(getResources().getString(R.string.edit));

            btnEdit.setLayoutParams(new LayoutParams(
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT));

            //Display delete button
            Button btnDelete = new Button(this);
            btnDelete.setText(getResources().getString(R.string.delete));

            btnDelete.setLayoutParams(new LayoutParams(
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT));


            tr.addView(name);
            tr.addView(type);
            tr.addView(btnEdit);
            tr.addView(btnDelete);

            catList.addView(tr, new TableLayout.LayoutParams(
                    LayoutParams.FILL_PARENT,
                    LayoutParams.WRAP_CONTENT));
        }

        mainLayout.addView(catList);


    }

This does not add anything to the layout. Any ideas why this does not work?

EDIT: Added the xml code here:

<?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/edit_cat"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1">

<TextView style="@style/pageHeader"
  android:text="@string/catEditor"/>

<Button
    android:id="@+id/btnNewCategory"
    android:text="@string/newCategory"
    android:textSize="11pt"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:onClick="onBtnClicked"/>
<Button
    android:id="@+id/back"
    android:text="@string/back"
    android:textSize="11pt"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:onClick="onBtnClicked"/>

</LinearLayout>

回答1:

Ok, I think I have an answer for you.

You need to be more specific when you are specifying LayoutParams. While it doesn't throw a compile exception, if you don't specify the correct parent class of the LayoutParams, nothing will show up.

When you specify layout params, you need to use the class of the container where the object is going. If you are setting the layout paramters of a textview that is going inside a LinearLayout, you would use new LinearLayout.LayoutParams(...) similarily if you are creating a textview to go inside a TableRow, you need to use TableRow.LayoutParams(...)

Below is the full code with minor modifications because I didn't have a db setup.

    LinearLayout mainLayout = (LinearLayout) findViewById(R.id.edit_cat);

    //Create table layout for the categories        
    TableLayout catList = new TableLayout(this);

    //Set the table layout to Match parent for both width and height
    // Note: We use LinearLayout.LayoutParams because the TableLayout is going inside a LinearLayout

    catList.setLayoutParams(
        new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));


    //Iterate the categories, and organize in tables      
    for(int i = 0; i < 5; i++)
    {
        TableRow tr = new TableRow(this);
        /* Since the table row is going inside a table layout, we specify the parameters using TableLayout.LayoutParams */
        tr.setLayoutParams(new TableLayout.LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT));

        //Display category name
        TextView name = new TextView(this);

        /* Since the TextView is going inside a TableRow, we use new TableRow.LayoutParams ... */
        name.setLayoutParams(new TableRow.LayoutParams(
                TableRow.LayoutParams.FILL_PARENT,
                TableRow.LayoutParams.WRAP_CONTENT));

        name.setText("Test Row - " + i);
        name.setBackgroundColor(Color.RED);


        //Display category type
        TextView type = new TextView(this);
        type.setText("Type Row - " + i);
        type.setBackgroundColor(Color.GREEN);
        type.setLayoutParams(new TableRow.LayoutParams(
                TableRow.LayoutParams.FILL_PARENT,
                TableRow.LayoutParams.WRAP_CONTENT));

        //Display edit button
        Button btnEdit = new Button(this);
        btnEdit.setText("Edit");

        btnEdit.setLayoutParams(new TableRow.LayoutParams(
                TableRow.LayoutParams.FILL_PARENT,
                TableRow.LayoutParams.WRAP_CONTENT));

        //Display delete button
        Button btnDelete = new Button(this);
        btnDelete.setText("Delete");

        btnDelete.setLayoutParams(new TableRow.LayoutParams(
                 TableRow.LayoutParams.FILL_PARENT,
                 TableRow.LayoutParams.WRAP_CONTENT));


        tr.addView(name);
        tr.addView(type);
        tr.addView(btnEdit);
        tr.addView(btnDelete);

        catList.addView(tr);
    }


    mainLayout.addView(catList);

来源：https://stackoverflow.com/questions/10286720/android-tablelayout-view-does-not-appear