Android TextView中显示彩虹字

一. 實現很簡單，就是對顏色進行線性的漸變。用到的類是LinearGradient.直接貼代碼：

public class Test extends Activity {
 private TextViewTest mTextViewTest;

 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  mTextViewTest = new TextViewTest(this);
  setContentView(mTextViewTest);
 }

 public class TextViewTest extends TextView {
  private LinearGradient mGradient;
  private int[] mGradientColors = { Color.RED, Color.rgb(255, 165, 0),
    Color.YELLOW, Color.GREEN, Color.rgb(0, 255, 255), Color.BLUE,
    Color.rgb(160, 32, 240) };
  private int mTitleWidth;
  private String mTitle = "三十六天罡,七十二地煞,乃是天地正邪之氣所生,如今奉命下凡轉世為科學家.但法用以正,則可以造福人群;";

  public TextViewTest(Context context) {
   super(context);
   // TODO Auto-generated constructor stub
   setLayoutParams(new LinearLayout.LayoutParams(
     LinearLayout.LayoutParams.FILL_PARENT,
     LinearLayout.LayoutParams.FILL_PARENT));
   setWillNotDraw(false);
  }

  @Override
  protected void onDraw(Canvas canvas) {
   // TODO Auto-generated method stub
   super.onDraw(canvas);
   measure(0, 0);
   
   Paint paint = new Paint();
   paint.setStyle(Style.FILL_AND_STROKE);
   mGradient = new LinearGradient(0, 0, getWidth(),
     getMeasuredHeight(), mGradientColors, null, TileMode.REPEAT);
   paint.setShader(mGradient);
   
   mTitleWidth = 0;
   float[] width = new float[mTitle.length()];
   paint.getTextWidths(mTitle, width);
   Log.i("Tag", "Width.length= " + width.length);
   int start = 0;
   int offsetY = 10;
   for (int j = 0; j < mTitle.length(); j++) {
    mTitleWidth += (int) Math.ceil(width[j]);
    if (mTitleWidth > getWidth()) {
     canvas.drawText(mTitle.substring(start, j), 0, offsetY,
       paint);
     mTitleWidth = 0;
     start = start + j;
     offsetY = offsetY + getMeasuredHeight() + 5;
     j--;
    }
   }
   if (mTitleWidth > 0) {
    canvas.drawText(mTitle.substring(start), 0, offsetY, paint);
   }
  }
 }
}

二. 實例圖

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