Have a problem on creating table Android Studio-CodePudding

I am trying to make a simple app. The program should create a table with given row and column numbers. I'm adding my Java and xml files below:

public class MainActivity extends AppCompatActivity {

    private Button btnCreate, btnCalculate, btnReset, btnExit;
    private EditText txtColumn, txtRow;
    private LinearLayout linLayout, mainLayout;
    private TextView txtResult;
    private Random random;


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

        btnCreate = (Button) findViewById(R.id.btnCreate);
        btnCalculate = (Button) findViewById(R.id.btnCalculate);
        btnReset = (Button) findViewById(R.id.btnReset);
        btnExit = (Button) findViewById(R.id.btnExit);

        txtColumn = (EditText) findViewById(R.id.txtColumn);
        txtRow = (EditText) findViewById(R.id.txtRow);
        txtResult = (TextView) findViewById(R.id.txtResult);
        txtColumn.requestFocus();

        random = new Random();

        LinearLayout mainLayout = findViewById(R.id.mainLayout);
        TableLayout table = new TableLayout(this);

        btnCalculate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            }
        });

        btnCreate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                table.setLayoutParams(new TableLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                table.setShrinkAllColumns(true);
                table.setStretchAllColumns(true);
                int columnNumber = Integer.parseInt(txtColumn.getText().toString());
                int rowNumber = Integer.parseInt(txtRow.getText().toString());

                for (int i=0; i < rowNumber; i  ) {
                    TableRow row = new TableRow(MainActivity.this);
                    for (int j=0; j < columnNumber; j  ) {
                        int value = random.nextInt(100)   1;
                        TextView tv = new TextView(MainActivity.this);
                        tv.setText(String.valueOf(value));
                        row.addView(tv);
                    }
                    table.addView(row);
                }

                mainLayout.addView(table);

            }
        });


        btnExit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                System.exit(0);
            }
        });
        btnReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                txtColumn.setText(null);
                txtRow.setText(null);
                txtResult.setText(null);
            }
        });
    }
}


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@ id/linLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >


    <EditText
        android:id="@ id/txtRow"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter row number"
        android:inputType="textCapWords"
        android:textSize="18sp" />

    <EditText
        android:id="@ id/txtColumn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter column number"
        android:inputType="textCapWords"
        android:textSize="18sp" />

    <TextView
        android:id="@ id/txtResult"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Result"
        android:background="#E91E63"
        android:textSize="18sp"
        />

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="horizontal" >

        <Button
            android:id="@ id/btnCreate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="CREATE"/>

        <Button
            android:id="@ id/btnCalculate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="CALCULATE" />

        <Button
            android:id="@ id/btnReset"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RESET" />
        <Button
            android:id="@ id/btnExit"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="EXIT" />
    </LinearLayout>

    <LinearLayout
        android:id="@ id/mainLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">


    </LinearLayout>

</LinearLayout>

This is the error message that I got:

The specified child already has a parent. You must call removeView() on the child's parent first.

Therefore, whenever I tried to add mainLayout.removeView(table); to the code nothing happens when I click the button create. Thank you all. I will be appreciated for any kinds of comments.

CodePudding user response：

You have the following errors:

1: The layout above the mainLayout layout is letting the height be match_parent. Make mainLayout not displayable.

2: The layout mainLayout is also setting the height to match_parent which is also wrong. I wonder do you understand what match_parent means?

3: The first time you add successfully, but because you are setting the height to match_parent, it makes it not visible, in fact it successfully added the table. The second click because it has been added to the table, it will crash.

The code below I have fixed for you, let's try it.

XML:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@ id/linLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >


    <EditText
        android:id="@ id/txtRow"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter row number"
        android:inputType="textCapWords"
        android:textSize="18sp"
        android:text="3"/>

    <EditText
        android:id="@ id/txtColumn"
        android:text="2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter column number"
        android:inputType="textCapWords"
        android:textSize="18sp" />

    <TextView
        android:id="@ id/txtResult"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Result"
        android:background="#E91E63"
        android:textSize="18sp"
        />

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@ id/btnCreate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="CREATE"/>

        <Button
            android:id="@ id/btnCalculate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="CALCULATE" />

        <Button
            android:id="@ id/btnReset"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RESET" />
        <Button
            android:id="@ id/btnExit"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="EXIT" />
    </LinearLayout>

    <LinearLayout
        android:id="@ id/mainLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">


    </LinearLayout>

</LinearLayout>

JAVA:

public class MainAct extends AppCompatActivity {

    private Button btnCreate, btnCalculate, btnReset, btnExit;
    private EditText txtColumn, txtRow;
    private LinearLayout linLayout, mainLayout;
    private TextView txtResult;
    private Random random;
    TableLayout table;

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

        btnCreate = (Button) findViewById(R.id.btnCreate);
        btnCalculate = (Button) findViewById(R.id.btnCalculate);
        btnReset = (Button) findViewById(R.id.btnReset);
        btnExit = (Button) findViewById(R.id.btnExit);

        txtColumn = (EditText) findViewById(R.id.txtColumn);
        txtRow = (EditText) findViewById(R.id.txtRow);
        txtResult = (TextView) findViewById(R.id.txtResult);
        txtColumn.requestFocus();

        random = new Random();

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


        btnCalculate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            }
        });

        btnCreate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (table != null) {
                    mainLayout.removeView(table);
                }
                table = new TableLayout(getBaseContext());

                table.setLayoutParams(new TableLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                table.setShrinkAllColumns(true);
                table.setStretchAllColumns(true);
                int columnNumber = Integer.parseInt(txtColumn.getText().toString());
                int rowNumber = Integer.parseInt(txtRow.getText().toString());

                for (int i=0; i < rowNumber; i  ) {
                    TableRow row = new TableRow(MainAct.this);
                    for (int j=0; j < columnNumber; j  ) {
                        int value = random.nextInt(100)   1;
                        TextView tv = new TextView(MainAct.this);
                        tv.setText(String.valueOf(value));
                        row.addView(tv);
                    }
                    table.addView(row);
                }
                if (table != null) {
                    mainLayout.addView(table);
                }
            }
        });


        btnExit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                System.exit(0);
            }
        });
        btnReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                txtColumn.setText(null);
                txtRow.setText(null);
                txtResult.setText(null);
            }
        });
    }
}