Android 自定义控件实现显示文字的功能

 public class printTextView extends TextView {  /**   * 字体显示出来的时间   */  private int DURATION = 8000;  public printTextView(Context context) {    this(context, null);  }  public printTextView(Context context, AttributeSet attrs) {    this(context, attrs, 0);  }  public printTextView(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);  }  public void printString(String str) {    if (str != null && str != "") {      // 字符串的长度      final int lenght = str.length();      final char[] c = new char[str.length()];      //将字符串转换成字符数组      for (int i = 0; i < str.length(); i++) {        c[i] = str.charAt(i);      }      ValueAnimator animator = ValueAnimator.ofFloat(0, 1);      animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {        @Override        public void onAnimationUpdate(ValueAnimator animation) {          // 字体显示的速度 v = 总的字体长度 / 总的显示时间          float v = (float) lenght / (float) DURATION;          // 动画执行速度          float fraction = (float) animation.getAnimatedValue();          //动画不同阶段字体应该显示的个数          int s = (int) (v * fraction * DURATION);          setText(c, 0, s);        }      });      animator.setDuration(DURATION);      animator.start();    }  }  }

 public class ScaleActivity extends AppCompatActivity {  private printTextView print_text;  String str = "我和你吻别,在无人的街.我和你吻别在狂乱的夜.这波给你103分," +      "多一分宽容,多一分耐心,更重要的是多一分父爱.";  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_scale);    initView();  }    print_text = (printTextView) findViewById(R.id.print_text);    print_text.printString(str);  }  }

 <?xml version="1.0" encoding="utf-8"?>  <LinearLayout xmlns:android="http://  schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:layout_margin="20dp"  android:orientation="vertical"  tools:context="com.example.customview.activity.ScaleActivity"> <com.example.customview.view.printTextView    android:id="@+id/print_text"    android:layout_width="match_parent"    android:layout_height="wrap_content" /> </LinearLayout>