在Android中遇到findViewById的问题

Question

I have a for loop which is running through an an array of imageView ID's that correspond to imageViews in my 'Board' class. The code is below:

for (String s : chunks) {                                                   
    String possibleSquare = "s" + s.substring(2, 4);                        
    ImageView backgroundImg = (ImageView) findViewById(R.id.possibleSquare);
    backgroundImg.setBackgroundColor(Color.rgb(255, 255, 255));   

I'm getting an error with findViewById and possibleSquare, specifically that Android 'cannot resolve' either.

Here is the xml:

<TextView
        android:id="@+id/BoardHeading"
        android:text="Chessboard"
        android:layout_width="300dp"
        android:layout_height="30dp"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:textColor="#ff2d3017"
        android:textSize="20dp"
        android:textAlignment="center" />

    <TableLayout
        android:layout_width="360dp"
        android:layout_height="320dp"
        android:layout_below="@id/BoardHeading"
        android:gravity="center_horizontal"
        android:background="#FFFFFF" >

    <TableRow
        android:id="@+id/tableRow1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >

        <ImageView
            android:id="@+id/s00"
            android:tag="black_rook"
            android:layout_width="0dp"
            android:layout_height="40dp"
            android:layout_weight="1"
            android:background="#F3E5AB"
            android:src="@drawable/black_rook"
            />

        <ImageView
            android:id="@+id/s01"
            android:tag="black_knight"
            android:layout_width="0dp"
            android:layout_height="40dp"
            android:background="#AF9B60"
            android:layout_weight="1"
            android:src="@drawable/black_knight"
        />

        <ImageView
            android:id="@+id/s02"
            android:tag="black_bishop"
            android:layout_width="0dp"
            android:layout_height="40dp"
            android:layout_weight="1"
            android:background="#F3E5AB"
            android:src="@drawable/black_bishop"
            />

And there are 61 more imageViews similar to the ones above.

The exact error I'm getting for the findViewById is: 'Cannot resolve method findViewById(?)

The error for the possibleSquare variable is 'Cannot resolve symbol possibleSquare'.

What am I doing wrong?

Answer 1

I think you're misunderstanding how objects work in Java. possibleSquare is a very different thing semantically than R.id.possibleSquare . I'm assuming you've given your views IDs that look like android:id="@+id/sSOMETHING"

for (String s : chunks) {                                                   
    String possibleSquare = "s" + s.substring(2, 4);
    int id = getResources().getIdentifier(possibleSquare, "id", getPackageName());                        
    ImageView backgroundImg = (ImageView) findViewById(id);
    backgroundImg.setBackgroundColor(Color.rgb(255, 255, 255));   
}

Note that if you're just looking to iterate over the TableRow , you could also do something like this:

TableRow tableRow = (TableRow)findViewById(R.id.tableRow1);
int childCount  = tableRow.getChildCount();
for (int i = 0; i < childCount; i++){
    ImageView backgroundImg = (ImageView) tableRow.getChildAt(i);
    backgroundImg.setBackgroundColor(Color.rgb(255, 255, 255));   
}

Answer 2

You can't do it that way as R.id.possibleSquare is essentially a variable name. It is not a string that you can use to replace content

You may want to look at this method

int resID = context.getResources().getIdentifier(possibleSquare, "id", PACKAGENAME);

It will try to match the string to a resource ID. I used it to constract the ResID of a drawable. Never used it for ID but it may work for you