判断是否安装支付宝

        pd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
            	
                Uri uri = Uri.parse("alipays://platformapi/startApp");
                Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                ComponentName componentName = intent.resolveActivity(getPackageManager());//componentName 值为空则没安装
                if (componentName == null){
                    Toast.makeText(MainActivity.this,"没有安装支付宝",Toast.LENGTH_SHORT).show();
                }else {
                    Toast.makeText(MainActivity.this,"安装支付宝了",Toast.LENGTH_SHORT).show();
                }
            }
        });