android如何获取textview最多显示

    /**
     * 获取textview最大能显示几个字
     * @param text 文本内容
     * @param size 文本字体大小
     * @param maxWidth textview的最大宽度
     * @return
     */
    private float getLineMaxNumber(String text, float size,float maxWidth) {
        if (null == text || "".equals(text)){
            return 0;
        }
        Paint paint = new Paint();
        paint.setTextSize(size);
        //得到文本内容总体长度
        float textWidth = paint.measureText(text);
        // textWidth
        float width = textWidth / text.length();
        float total = maxWidth / width;
        return total;
    }

/**
     * 获取textview一行最大能显示几个字(需要在TextView测量完成之后)
     *
     * @param text     文本内容
     * @param paint    textview.getPaint()
     * @param maxWidth textview.getMaxWidth()/或者是指定的数值,如200dp
     */
    private int getLineMaxNumber(String text, TextPaint paint, int maxWidth) {
        if (null == text || "".equals(text)) {
            return 0;
        }
        StaticLayout staticLayout = new StaticLayout(text, paint, maxWidth, Layout.Alignment.ALIGN_NORMAL
                , 1.0f, 0, false);
        //获取第一行最后显示的字符下标
        return staticLayout.getLineEnd(0);
    }

  <TextView
        android:id="@+id/textView"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:ellipsize="end"
        android:singleLine="true" />

String str = "If you really want to hear about it, the first thing you'll probably want to know";
这样就会导致显示不全，像这样：
If you really want to hear about it, the first thin...

所以，如果你想得到已显示的字符个数，或者未显示的字符个数，那么其中的关键是如何计算每一个字符的宽度。
然后遍历这个字符串，当前n个字符宽度总和，超过TextView宽度时，就得到了已显示的字符个数。

String str = "If you really want to hear about it, the first thing you'll probably want to know";
mTextView = (TextView) findViewById(R.id.textView);

// 计算TextView宽度：xml中定义的宽度300dp，转换成px
float textViewWidth = convertDpToPixel(300);
float dotWidth = getCharWidth(mTextView, '.');
Log.d(TAG, "TextView width " + textViewWidth);

int sumWidth = 0;
for (int index=0; index<str.length(); index++) {
    // 计算每一个字符的宽度
    char c = str.charAt(index);
    float charWidth = getCharWidth(mTextView, c);
    sumWidth += charWidth;
    Log.d(TAG, "#" + index + ": " + c + ", width=" + charWidth + ", sum=" + sumWidth);
    
    if (sumWidth + dotWidth*3 >= textViewWidth) {
        Log.d(TAG, "TextView shows #" + index + " char: " + str.substring(0, index));
        break;
    }
}

// Dp转Px
private float convertDpToPixel(float dp){
    Resources resources = getResources();
    DisplayMetrics metrics = resources.getDisplayMetrics();
    float px = dp * (metrics.densityDpi / 160f);
    return px;
}

// 计算每一个字符的宽度
public float getCharWidth(TextView textView, char c) {
    textView.setText(String.valueOf(c));
    textView.measure(0, 0);
    return textView.getMeasuredWidth();
}