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.
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);
}
});
}
}